Method and user equipment for transmitting random access channel signal, and method and base station for receiving random access channel signal

ABSTRACT

A user equipment in a wireless communication system receives RACH configuration information including preamble format information indicating a first format and transmits a RACH preamble with the first format. The RACH preamble with the first format includes a cyclic prefix (CP) part and a sequence part in a time domain. The RACH preamble with the first format satisfies: a CP length of the RACH preamble of the first format is N times a CP length NCP of an orthogonal frequency division multiplexing (OFDM) symbol, where N is the number of OFDM symbols used to transmit a RACH preamble and is greater than 1.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371of International Application No. PCT/KR2018/004959, filed on Apr. 27,2018, which claims the benefit of U.S. Provisional Application No.62/501,086, filed on May 3, 2017, U.S. Provisional Application No.62/507,752, filed on May 17, 2017, U.S. Provisional Application No.62/517,198, filed on Jun. 9, 2017, and U.S. Provisional Application No.62/535,941, filed on Jul. 23, 2017. The disclosures of the priorapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system. Moreparticularly, the present invention relates to a method and apparatusfor transmitting/receiving a random access channel (RACH) signal.

BACKGROUND ART

With appearance and spread of machine-to-machine (M2M) communication anda variety of devices such as smartphones and tablet PCs and technologydemanding a large amount of data transmission, data throughput needed ina cellular network has rapidly increased. To satisfy such rapidlyincreasing data throughput, carrier aggregation technology, cognitiveradio technology, etc. for efficiently employing more frequency bandsand multiple input multiple output (MIMO) technology, multi-base station(BS) cooperation technology, etc. for raising data capacity transmittedon limited frequency resources have been developed.

A general wireless communication system performs datatransmission/reception through one downlink (DL) band and through oneuplink (UL) band corresponding to the DL band (in case of a frequencydivision duplex (FDD) mode), or divides a prescribed radio frame into aUL time unit and a DL time unit in the time domain and then performsdata transmission/reception through the UL/DL time unit (in case of atime division duplex (TDD) mode). A base station (BS) and a userequipment (UE) transmit and receive data and/or control informationscheduled on a prescribed time unit basis, e.g. on a subframe basis. Thedata is transmitted and received through a data region configured in aUL/DL subframe and the control information is transmitted and receivedthrough a control region configured in the UL/DL subframe. To this end,various physical channels carrying radio signals are formed in the UL/DLsubframe. In contrast, carrier aggregation technology serves to use awider UL/DL bandwidth by aggregating a plurality of UL/DL frequencyblocks in order to use a broader frequency band so that more signalsrelative to signals when a single carrier is used can be simultaneouslyprocessed.

In addition, a communication environment has evolved into increasingdensity of nodes accessible by a user at the periphery of the nodes. Anode refers to a fixed point capable of transmitting/receiving a radiosignal to/from the UE through one or more antennas. A communicationsystem including high-density nodes may provide a better communicationservice to the UE through cooperation between the nodes.

As more communication devices have demanded higher communicationcapacity, there has been necessity of enhanced mobile broadband (eMBB)relative to legacy radio access technology (RAT). In addition, massivemachine type communication (mMTC) for providing various services anytimeand anywhere by connecting a plurality of devices and objects to eachother is one main issue to be considered in future-generationcommunication.

Further, a communication system to be designed in consideration ofservices/UEs sensitive to reliability and latency is under discussion.The introduction of future-generation RAT has been discussed by takinginto consideration eMBB communication, mMTC, ultra-reliable andlow-latency communication (URLLC), and the like.

DISCLOSURE Technical Problem

Due to introduction of new radio communication technology, the number ofuser equipments (UEs) to which a BS should provide a service in aprescribed resource region increases and the amount of data and controlinformation that the BS should transmit to the UEs increases. Since theamount of resources available to the BS for communication with the UE(s)is limited, a new method in which the BS efficiently receives/transmitsuplink/downlink data and/or uplink/downlink control information usingthe limited radio resources is needed.

With development of technologies, overcoming delay or latency has becomean important challenge. Applications whose performance criticallydepends on delay/latency are increasing. Accordingly, a method to reducedelay/latency compared to the legacy system is demanded.

In addition, a signal transmission/reception method is required in thesystem supporting new radio access technologies using high frequencybands.

The technical objects that can be achieved through the present inventionare not limited to what has been particularly described hereinabove andother technical objects not described herein will be more clearlyunderstood by persons skilled in the art from the following detaileddescription.

Technical Solution

According to an aspect of the present invention, provided herein is amethod of transmitting a random access channel (RACH) signal by a userequipment in a wireless communication system. The method includesreceiving RACH configuration information including preamble formatinformation indicating a first format; and transmitting a RACH preamblewith the first format. The RACH preamble with the first format includesa cyclic prefix (CP) part and a sequence part in a time domain. The RACHpreamble with the first format satisfies: a CP length of the RACHpreamble with the first format is N times a CP length N_(CP) of anorthogonal frequency division multiplexing (OFDM) symbol, where N is thenumber of OFDM symbols used for transmission of a RACH preamble and isgreater than 1.

According to another aspect of the present invention, provided herein isa user equipment for transmitting a random access channel (RACH) signalin a wireless communication system. The user equipment includes atransceiver, and a processor configured to control the transceiver. Theprocessor is configured to: control the transceiver to receive RACHconfiguration information including preamble format informationindicating a first format; and control the transceiver to transmit aRACH preamble with the first format. The RACH preamble with the firstformat includes a cyclic prefix (CP) part and a sequence part in a timedomain. The RACH preamble with the first format satisfies: a CP lengthof the RACH preamble with the first format is N times a CP length N_(CP)of an orthogonal frequency division multiplexing (OFDM) symbol, where Nis the number of OFDM symbols used for transmission of a RACH preambleand is greater than 1.

According to another aspect of the present invention, provided herein isa method of receiving a random access channel (RACH) signal by a basestation in a wireless communication system. The method includestransmitting RACH configuration information including preamble formatinformation indicating a first format; and detecting a RACH preamblewith the first format. The RACH preamble with the first format includesa cyclic prefix (CP) part and a sequence part in a time domain. The RACHpreamble of the first format satisfies: a CP length of the RACH preamblewith the first format is N times a CP length N_(CP) of an orthogonalfrequency division multiplexing (OFDM) symbol, where N is the number ofOFDM symbols used for transmission of a RACH preamble and is greaterthan 1.

According to another aspect of the present invention, provided herein isa base station for receiving a random access channel (RACH) signal in awireless communication system. The base station includes a transceiver,and a processor configured to control the transceiver. The processor isconfigured to: control the transceiver to transmit RACH configurationinformation including preamble format information indicating a firstformat; and detect a RACH preamble with the first format. The RACHpreamble with the first format includes a cyclic prefix (CP) part and asequence part in a time domain. The RACH preamble with the first formatsatisfies: a CP length of the RACH preamble with the first format is Ntimes a CP length N_(CP) of an orthogonal frequency divisionmultiplexing (OFDM) symbol, where N is the number of OFDM symbols usedfor transmission of a RACH preamble and is greater than 1.

In each aspect of the present invention, a length of the RACH preamblewith the first format may be equal to a total length of OFDM symbolsused for transmission of the RACH preamble of the first format.

In each aspect of the present invention, the first format may be apreamble format comprised of a CP part having a length of N*144*T_(s)and a sequence part having a length of N*2048*T_(s), where T_(s) is asampling time.

In each aspect of the present invention, 144*T_(s) may be equal toN_(CP) and 2048*T_(s) may be equal to a length of a data part per OFDMsymbol.

In each aspect of the present invention, the first format may be apreamble format having N being 2, 4, or 6.

In each aspect of the present invention, the sequence part may include aZadoff-Chu sequence having a length of 139, N times.

In each aspect of the present invention, the RACH configurationinformation may further include information about a slot used for aRACH.

In each aspect of the present invention, when the preamble formatinformation indicates a combination of the first preamble format and asecond preamble format, the user equipment may transmit the RACHpreamble with the first format in a RACH resource associated with asynchronization signal (SS) block detected by the user equipment amongRACH resources of the slot if the associated RACH resource is not a lastRACH resource of the slot in the time domain and transmit a RACHpreamble with the second format in the associated RACH resource if theassociated RACH resource is the last RACH resource of the slot.

In each aspect of the present invention, if the preamble formatinformation indicates a combination of the first preamble format and asecond preamble format, the base station may attempt to detect the RACHpreamble with the first format in a RACH resource other than a last RACHresource of the slot in the time domain among RACH resources of the slotand attempt to detect a RACH preamble with the second format in the lastRACH resource.

In each aspect of the present invention, the second format may be apreamble format including a guard time with no signal after a sequencepart in the RACH preamble with the second format.

The above technical solutions are merely some parts of the embodimentsof the present invention and various embodiments into which thetechnical features of the present invention are incorporated can bederived and understood by persons skilled in the art from the followingdetailed description of the present invention.

Advantageous Effects

According to the present invention, a random access channel suitable foran NR system can be transmitted by a UE and received by a BS. The randomaccess channel can be efficiently transmitted/received and thereforethroughput of the NR system can be improved.

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a random access preamble format in a legacy LTE/LTE-Asystem.

FIG. 2 illustrates a slot structure available in a new radio accesstechnology (NR).

FIG. 3 abstractly illustrates transceiver units (TXRUs) and a hybridbeamforming structure in terms of physical antennas.

FIG. 4 illustrates a cell of a new radio access technology (NR) system.

FIG. 5 illustrates transmission of a synchronization signal (SS) blockand a RACH resource linked to the SS block.

FIG. 6 illustrates configuration/format of a random access channel(RACH) preamble and a receiver function.

FIG. 7 illustrates a reception (Rx) beam formed at a gNB to receive aRACH preamble.

FIG. 8 illustrates a RACH signal and a RACH resource to explain termsused to describe the present invention.

FIG. 9 illustrates a RACH resource set.

FIG. 10 illustrates boundary alignment of a RACH resource according tothe present invention.

FIG. 11 illustrates a method of configuring a mini slot within a RACHslot SLOT_(RACH) when BC holds.

FIG. 12 illustrates another method of configuring a mini slot within aRACH slot SLOT_(RACH) when BC holds.

FIG. 13 illustrates a method of configuring a mini slot within a RACHslot SLOT_(RACH) when beam correspondence (BC) does not hold.

FIG. 14 illustrates a method of configuring a mini slot using a guardtime.

FIG. 15 illustrates an example of transmitting data by performing minislot concatenation with the same length as a normal slot when BC holds.

FIGS. 16 and 17 illustrate RACH resource configuration in the timedomain.

FIG. 18 illustrates RACH time resource information.

FIG. 19 illustrates an example of allocating RACH preamble sequences.

FIG. 20 illustrates a RACH resource block.

FIG. 21 illustrates a RACH configuration duration according to thepresent invention.

FIG. 22 illustrates a configuration of each RACH resource within a RACHresource block.

FIG. 23 illustrates a slot structure.

FIG. 24 illustrates a RACH preamble format in an OFDM symbol.

FIGS. 25 and 26 illustrate alignment of RACH preambles in a slot.

FIG. 27 illustrates RACH preamble formats for aligning a RACH preambleand a symbol boundary by increasing a CP length according to the presentinvention.

FIG. 28 illustrates a RACH resource in a slot consisting of 7 symbolsand RACH preamble mapping according to the number of preamblerepetitions.

FIG. 29 illustrates a null OFDM symbol located after a RACH symbol.

FIG. 30 illustrates a method of multiplexing RACH resources in a slot.

FIG. 31 illustrates a transmission format of a RACH preamble of a2-symbol length aligned with two symbols.

FIG. 32 illustrates preamble formats corresponding to preamble format 1of Table 9.

FIGS. 33 to 35 illustrate locations of RACH resources in a slotaccording to RACH slot types.

FIG. 36 is a block diagram illustrating elements of a transmittingdevice 10 and a receiving device 20 for implementing the presentinvention.

MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the invention. Thefollowing detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details.

In some instances, known structures and devices are omitted or are shownin block diagram form, focusing on important features of the structuresand devices, so as not to obscure the concept of the present invention.The same reference numbers will be used throughout this specification torefer to the same or like parts.

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE. For convenience of description, it is assumed thatthe present invention is applied to 3GPP based communication system,e.g. LTE/LTE-A, NR. However, the technical features of the presentinvention are not limited thereto. For example, although the followingdetailed description is given based on a mobile communication systemcorresponding to a 3GPP LTE/LTE-A/NR system, aspects of the presentinvention that are not specific to 3GPP LTE/LTE-A/NR are applicable toother mobile communication systems.

For example, the present invention is applicable to contention basedcommunication such as Wi-Fi as well as non-contention basedcommunication as in the 3GPP LTE/LTE-A system in which an eNB allocatesa DL/UL time/frequency resource to a UE and the UE receives a DL signaland transmits a UL signal according to resource allocation of the eNB.In a non-contention based communication scheme, an access point (AP) ora control node for controlling the AP allocates a resource forcommunication between the UE and the AP, whereas, in a contention basedcommunication scheme, a communication resource is occupied throughcontention between UEs which desire to access the AP. The contentionbased communication scheme will now be described in brief. One type ofthe contention based communication scheme is carrier sense multipleaccess (CSMA). CSMA refers to a probabilistic media access control (MAC)protocol for confirming, before a node or a communication devicetransmits traffic on a shared transmission medium (also called a sharedchannel) such as a frequency band, that there is no other traffic on thesame shared transmission medium. In CSMA, a transmitting devicedetermines whether another transmission is being performed beforeattempting to transmit traffic to a receiving device. In other words,the transmitting device attempts to detect presence of a carrier fromanother transmitting device before attempting to perform transmission.Upon sensing the carrier, the transmitting device waits for anothertransmission device which is performing transmission to finishtransmission, before performing transmission thereof. Consequently, CSMAcan be a communication scheme based on the principle of “sense beforetransmit” or “listen before talk”. A scheme for avoiding collisionbetween transmitting devices in the contention based communicationsystem using CSMA includes carrier sense multiple access with collisiondetection (CSMA/CD) and/or carrier sense multiple access with collisionavoidance (CSMA/CA). CSMA/CD is a collision detection scheme in a wiredlocal area network (LAN) environment. In CSMA/CD, a personal computer(PC) or a server which desires to perform communication in an Ethernetenvironment first confirms whether communication occurs on a networkand, if another device carries data on the network, the PC or the serverwaits and then transmits data. That is, when two or more users (e.g.PCs, UEs, etc.) simultaneously transmit data, collision occurs betweensimultaneous transmission and CSMA/CD is a scheme for flexiblytransmitting data by monitoring collision. A transmitting device usingCSMA/CD adjusts data transmission thereof by sensing data transmissionperformed by another device using a specific rule. CSMA/CA is a MACprotocol specified in IEEE 802.11 standards. A wireless LAN (WLAN)system conforming to IEEE 802.11 standards does not use CSMA/CD whichhas been used in IEEE 802.3 standards and uses CA, i.e. a collisionavoidance scheme. Transmission devices always sense carrier of a networkand, if the network is empty, the transmission devices wait fordetermined time according to locations thereof registered in a list andthen transmit data. Various methods are used to determine priority ofthe transmission devices in the list and to reconfigure priority. In asystem according to some versions of IEEE 802.11 standards, collisionmay occur and, in this case, a collision sensing procedure is performed.A transmission device using CSMA/CA avoids collision between datatransmission thereof and data transmission of another transmissiondevice using a specific rule.

In embodiments of the present invention described below, the term“assume” may mean that a subject to transmit a channel transmits thechannel in accordance with the corresponding “assumption”. This may alsomean that a subject to receive the channel receives or decodes thechannel in a form conforming to the “assumption”, on the assumption thatthe channel has been transmitted according to the “assumption”.

In the present invention, puncturing a channel on a specific resourcemeans that the signal of the channel is mapped to the specific resourcein the procedure of resource mapping of the channel, but a portion ofthe signal mapped to the punctured resource is excluded in transmittingthe channel. In other words, the specific resource which is punctured iscounted as a resource for the channel in the procedure of resourcemapping of the channel, a signal mapped to the specific resource amongthe signals of the channel is not actually transmitted. The receiver ofthe channel receives, demodulates or decodes the channel, assuming thatthe signal mapped to the specific resource is not transmitted. On theother hand, rate-matching of a channel on a specific resource means thatthe channel is never mapped to the specific resource in the procedure ofresource mapping of the channel, and thus the specific resource is notused for transmission of the channel. In other words, the rate-matchedresource is not counted as a resource for the channel in the procedureof resource mapping of the channel. The receiver of the channelreceives, demodulates, or decodes the channel, assuming that thespecific rate-matched resource is not used for mapping and transmissionof the channel.

In the present invention, a user equipment (UE) may be a fixed or mobiledevice. Examples of the UE include various devices that transmit andreceive user data and/or various kinds of control information to andfrom a base station (BS). The UE may be referred to as a terminalequipment (TE), a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, a personaldigital assistant (PDA), a wireless modem, a handheld device, etc. Inaddition, in the present invention, a BS generally refers to a fixedstation that performs communication with a UE and/or another BS, andexchanges various kinds of data and control information with the UE andanother BS. The BS may be referred to as an advanced base station (ABS),a node-B (NB), an evolved node-B (eNB), a base transceiver system (BTS),an access point (AP), a processing server (PS), etc. Particularly, a BSof a UTRAN is referred to as a Node-B, a BS of an E-UTRAN is referred toas an eNB, and a BS of a new radio access technology network is referredto as a gNB. In describing the present invention, a BS will be referredto as a gNB.

In the present invention, a node refers to a fixed point capable oftransmitting/receiving a radio signal through communication with a UE.Various types of gNBs may be used as nodes irrespective of the termsthereof. For example, a BS, a node B (NB), an e-node B (eNB), apico-cell eNB (PeNB), a home eNB (HeNB), gNB, a relay, a repeater, etc.may be a node. In addition, the node may not be a gNB. For example, thenode may be a radio remote head (RRH) or a radio remote unit (RRU). TheRRH or RRU generally has a lower power level than a power level of agNB. Since the RRH or RRU (hereinafter, RRH/RRU) is generally connectedto the gNB through a dedicated line such as an optical cable,cooperative communication between RRH/RRU and the gNB can be smoothlyperformed in comparison with cooperative communication between gNBsconnected by a radio line. At least one antenna is installed per node.The antenna may mean a physical antenna or mean an antenna port or avirtual antenna.

In the present invention, a cell refers to a prescribed geographicalarea to which one or more nodes provide a communication service.Accordingly, in the present invention, communicating with a specificcell may mean communicating with a gNB or a node which provides acommunication service to the specific cell. In addition, a DL/UL signalof a specific cell refers to a DL/UL signal from/to a gNB or a nodewhich provides a communication service to the specific cell. A nodeproviding UL/DL communication services to a UE is called a serving nodeand a cell to which UL/DL communication services are provided by theserving node is especially called a serving cell. Furthermore, channelstatus/quality of a specific cell refers to channel status/quality of achannel or communication link formed between a gNB or node whichprovides a communication service to the specific cell and a UE. In the3GPP based communication system, the UE may measure DL channel statereceived from a specific node using cell-specific reference signal(s)(CRS(s)) transmitted on a CRS resource and/or channel state informationreference signal(s) (CSI-RS(s)) transmitted on a CSI-RS resource,allocated by antenna port(s) of the specific node to the specific node.

Meanwhile, a 3GPP based communication system uses the concept of a cellin order to manage radio resources and a cell associated with the radioresources is distinguished from a cell of a geographic region.

A “cell” of a geographic region may be understood as coverage withinwhich a node can provide service using a carrier and a “cell” of a radioresource is associated with bandwidth (BW) which is a frequency rangeconfigured by the carrier. Since DL coverage, which is a range withinwhich the node is capable of transmitting a valid signal, and ULcoverage, which is a range within which the node is capable of receivingthe valid signal from the UE, depends upon a carrier carrying thesignal, the coverage of the node may be associated with coverage of the“cell” of a radio resource used by the node. Accordingly, the term“cell” may be used to indicate service coverage of the node sometimes, aradio resource at other times, or a range that a signal using a radioresource can reach with valid strength at other times.

Meanwhile, the 3GPP communication standards use the concept of a cell tomanage radio resources. The “cell” associated with the radio resourcesis defined by combination of downlink resources and uplink resources,that is, combination of DL CC and UL CC. The cell may be configured bydownlink resources only, or may be configured by downlink resources anduplink resources. If carrier aggregation is supported, linkage between acarrier frequency of the downlink resources (or DL CC) and a carrierfrequency of the uplink resources (or UL CC) may be indicated by systeminformation. For example, combination of the DL resources and the ULresources may be indicated by linkage of system information block type 2(SIB2). The carrier frequency means a center frequency of each cell orCC. A cell operating on a primary frequency may be referred to as aprimary cell (Pcell) or PCC, and a cell operating on a secondaryfrequency may be referred to as a secondary cell (Scell) or SCC. Thecarrier corresponding to the Pcell on downlink will be referred to as adownlink primary CC (DL PCC), and the carrier corresponding to the Pcellon uplink will be referred to as an uplink primary CC (UL PCC). A Scellmeans a cell that may be configured after completion of radio resourcecontrol (RRC) connection establishment and used to provide additionalradio resources. The Scell may form a set of serving cells for the UEtogether with the Pcell in accordance with capabilities of the UE. Thecarrier corresponding to the Scell on the downlink will be referred toas downlink secondary CC (DL SCC), and the carrier corresponding to theScell on the uplink will be referred to as uplink secondary CC (UL SCC).Although the UE is in RRC-CONNECTED state, if it is not configured bycarrier aggregation or does not support carrier aggregation, a singleserving cell configured by the Pcell only exists.

3GPP based communication standards define DL physical channelscorresponding to resource elements carrying information derived from ahigher layer and DL physical signals corresponding to resource elementswhich are used by a physical layer but which do not carry informationderived from a higher layer. For example, a physical downlink sharedchannel (PDSCH), a physical broadcast channel (PBCH), a physicalmulticast channel (PMCH), a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), and a physicalhybrid ARQ indicator channel (PHICH) are defined as the DL physicalchannels, and a reference signal and a synchronization signal aredefined as the DL physical signals. A reference signal (RS), also calleda pilot, refers to a special waveform of a predefined signal known toboth a BS and a UE. For example, a cell-specific RS (CRS), a UE-specificRS (UE-RS), a positioning RS (PRS), and channel state information RS(CSI-RS) may be defined as DL RSs. Meanwhile, the 3GPP LTE/LTE-Astandards define UL physical channels corresponding to resource elementscarrying information derived from a higher layer and UL physical signalscorresponding to resource elements which are used by a physical layerbut which do not carry information derived from a higher layer. Forexample, a physical uplink shared channel (PUSCH), a physical uplinkcontrol channel (PUCCH), and a physical random access channel (PRACH)are defined as the UL physical channels, and a demodulation referencesignal (DM RS) for a UL control/data signal and a sounding referencesignal (SRS) used for UL channel measurement are defined as the ULphysical signals.

In the present invention, a physical downlink control channel (PDCCH), aphysical control format indicator channel (PCFICH), a physical hybridautomatic retransmit request indicator channel (PHICH), and a physicaldownlink shared channel (PDSCH) refer to a set of time-frequencyresources or resource elements (REs) carrying downlink controlinformation (DCI), a set of time-frequency resources or REs carrying acontrol format indicator (CFI), a set of time-frequency resources or REscarrying downlink acknowledgement (ACK)/negative ACK (NACK), and a setof time-frequency resources or REs carrying downlink data, respectively.In addition, a physical uplink control channel (PUCCH), a physicaluplink shared channel (PUSCH) and a physical random access channel(PRACH) refer to a set of time-frequency resources or REs carryinguplink control information (UCI), a set of time-frequency resources orREs carrying uplink data and a set of time-frequency resources or REscarrying random access signals, respectively. In the present invention,in particular, a time-frequency resource or RE that is assigned to orbelongs to PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to asPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH time-frequency resource,respectively. Therefore, in the present invention, PUCCH/PUSCH/PRACHtransmission of a UE is conceptually identical to UCI/uplink data/randomaccess signal transmission on PUSCH/PUCCH/PRACH, respectively. Inaddition, PDCCH/PCFICH/PHICH/PDSCH transmission of a gNB is conceptuallyidentical to downlink data/DCI transmission on PDCCH/PCFICH/PHICH/PDSCH,respectively.

Hereinafter, OFDM symbol/subcarrier/RE to or for whichCRS/DMRS/CSI-RS/SRS/UE-RS/TRS is assigned or configured will be referredto as CRS/DMRS/CSI-RS/SRS/UE-RS/TRS symbol/carrier/subcarrier/RE. Forexample, an OFDM symbol to or for which a tracking RS (TRS) is assignedor configured is referred to as a TRS symbol, a subcarrier to or forwhich the TRS is assigned or configured is referred to as a TRSsubcarrier, and an RE to or for which the TRS is assigned or configuredis referred to as a TRS RE. In addition, a subframe configured fortransmission of the TRS is referred to as a TRS subframe. Moreover, asubframe in which a broadcast signal is transmitted is referred to as abroadcast subframe or a PBCH subframe and a subframe in which asynchronization signal (e.g. PSS and/or SSS) is transmitted is referredto a synchronization signal subframe or a PSS/SSS subframe. OFDMsymbol/subcarrier/RE to or for which PSS/SSS is assigned or configuredis referred to as PSS/SSS symbol/subcarrier/RE, respectively.

In the present invention, a CRS port, a UE-RS port, a CSI-RS port, and aTRS port refer to an antenna port configured to transmit a CRS, anantenna port configured to transmit a UE-RS, an antenna port configuredto transmit a CSI-RS, and an antenna port configured to transmit a TRS,respectively. Antenna ports configured to transmit CRSs may bedistinguished from each other by the locations of REs occupied by theCRSs according to CRS ports, antenna ports configured to transmit UE-RSsmay be distinguished from each other by the locations of REs occupied bythe UE-RSs according to UE-RS ports, and antenna ports configured totransmit CSI-RSs may be distinguished from each other by the locationsof REs occupied by the CSI-RSs according to CSI-RS ports. Therefore, theterm CRS/UE-RS/CSI-RS/TRS ports may also be used to indicate a patternof REs occupied by CRSs/UE-RSs/CSI-RSs/TRSs in a predetermined resourceregion. In the present invention, both a DMRS and a UE-RS refer to RSsfor demodulation and, therefore, the terms DMRS and UE-RS are used torefer to RSs for demodulation.

For terms and technologies which are not described in detail in thepresent invention, reference can be made to the standard document of3GPP LTE/LTE-A, for example, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS36.213, 3GPP TS 36.321, and 3GPP TS 36.331 and the standard document of3GPP NR, for example, 3GPP TS 38.211, 3GPP TS 38.212, 3GPP 38.213, 3GPP38.214, 3GPP 38.215, 3GPP TS 38.321, and 3GPP TS 36.331.

In an LTE/LTE-A system, when a UE is powered on or desires to access anew cell, the UE perform an initial cell search procedure includingacquiring time and frequency synchronization with the cell and detectinga physical layer cell identity N^(cell) _(ID) of the cell. To this end,the UE may receive synchronization signals, for example, a primarysynchronization signal (PSS) and a secondary synchronization signal(SSS), from an eNB to thus establish synchronization with the eNB andacquire information such as a cell identity (ID). After the initial cellsearch procedure, the UE may perform a random access procedure tocomplete access to the eNB. To this end, the UE may transmit a preamblethrough a physical random access channel (PRACH) and receive a responsemessage to the preamble through a PDCCH and a PDSCH. After performingthe aforementioned procedures, the UE may perform PDCCH/PDSCH receptionand PUSCH/PUCCH transmission as a normal UL/DL transmission procedure.The random access procedure is also referred to as a random accesschannel (RACH) procedure. The random access procedure is used forvarious purposes including initial access, adjustment of ULsynchronization, resource assignment, and handover.

After transmitting the RACH preamble, the UE attempts to receive arandom access response (RAR) within a preset time window. Specifically,the UE attempts to detect a PDCCH with a random access radio networktemporary identifier (RA-RNTI) (hereinafter, RA-RNTI PDCCH) (e.g., CRCis masked with RA-RNTI on the PDCCH) in the time window. In detectingthe RA-RNTI PDCCH, the UE checks the PDSCH corresponding to the RA-RNTIPDCCH for presence of an RAR directed thereto. The RAR includes timingadvance (TA) information indicating timing offset information for ULsynchronization, UL resource allocation information (UL grantinformation), and a temporary UE identifier (e.g., temporary cell-RNTI(TC-RNTI)). The UE may perform UL transmission (of, e.g., Msg3)according to the resource allocation information and the TA value in theRAR. HARQ is applied to UL transmission corresponding to the RAR.Accordingly, after transmitting Msg3, the UE may receive acknowledgementinformation (e.g., PHICH) corresponding to Msg3.

FIG. 1 illustrates a random access preamble format in a legacy LTE/LTE-Asystem.

In the legacy LTE/LTE-A system, a random access preamble, i.e., a RACHpreamble, includes a cyclic prefix having a length T_(CP) and a sequencepart having a length T_(SEQ) in a physical layer. The parameter valuesT_(CP) and T_(SEQ) are listed in the following table, and depend on theframe structure and the random access configuration. Higher layerscontrol the preamble format. In the 3GPP LTE/LTE-A system, PRACHconfiguration information is signaled through system information andmobility control information of a cell. The PRACH configurationinformation indicates a root sequence index, a cyclic shift unit N_(CS)of a Zadoff-Chu sequence, the length of the root sequence, and apreamble format, which are to be used for a RACH procedure in the cell.In the 3GPP LTE/LTE-A system, a PRACH opportunity, which is a timing atwhich the preamble format and the RACH preamble may be transmitted, isindicated by a PRACH configuration index, which is a part of the RACHconfiguration information (refer to Section 5.7 of 3GPP TS 36.211 and“PRACH-Config” of 3GPP TS 36.331). The length of the Zadoff-Chu sequenceused for the RACH preamble is determined according to the preambleformat (refer to Table 4)

TABLE 1 Preamble format T_(CP) T_(SEQ) 0 3168 · T_(s) 24576 · T_(s) 121024 · T_(s  ) 24576 · T_(s) 2 6240 · T_(s) 2 · 24576 · T_(s   ) 321024 · T_(s  ) 2 · 24576 · T_(s   ) 4  448 · T_(s)   4096 · T_(s)

In the LTE/LTE-A system, the RACH preamble is transmitted in a ULsubframe. The transmission of a random access preamble is restricted tocertain time and frequency resources. These resources are called PRACHresources, and enumerated in increasing order of the subframe numberwithin the radio frame and the PRBs in the frequency domain such thatindex 0 correspond to the lowest numbered PRB and subframe within theradio frame. Random access resources are defined according to the PRACHconfiguration index (refer to the standard document of 3GPP TS 36.211).The PRACH configuration index is given by a higher layer signal(transmitted by an eNB).

The sequence part of the RACH preamble (hereinafter, preamble sequence)uses a Zadoff-Chu sequence. The preamble sequences for RACH aregenerated from Zadoff-Chu sequences with zero correlation zone,generated from one or several root Zadoff-Chu sequences. The networkconfigures the set of preamble sequences the UE is allowed to use. Inthe legacy LTE/LTE-A system, there are 64 preambles available in eachcell. The set of 64 preamble sequences in a cell is found by includingfirst, in the order of increasing cyclic shift, all the available cyclicshifts of a root Zadoff-Chu sequence with the logical index RACH ROOTSEQUENCE, where RACH ROOT SEQUENCE is broadcasted as part of the systeminformation. Additional preamble sequences, in case 64 preambles cannotbe generated from a single root Zadoff-Chu sequence, are obtained fromthe root sequences with the consecutive logical indexes until all the 64sequences are found. The logical root sequence order is cyclic: thelogical index 0 is consecutive to 837. The relation between a logicalroot sequence index and physical root sequence index u is given by Table2 and Table 3 for preamble formats 0-3 and 4, respectively.

TABLE 2 Logical root sequence Physical root sequence number u (inincreasing order number of  

  corresponding logical sequnce number)  0~23 129, 710, 140, 699, 120,719, 210, 629, 168, 671, 84, 755, 105, 734, 93, 746, 70, 769, 60, 779,2, 837, 1, 838 24~29 56, 783, 112, 727, 148, 691 30~35 80, 759, 42, 797,40, 799 36~41 35, 804, 73, 766, 146, 693 42~51 31, 808, 28, 811, 30,809, 27, 812, 29, 810 52~63 24, 815, 48, 791, 68, 771, 74, 765, 178,661, 136, 703 64~75 86, 753, 78, 761, 43, 796, 39, 800, 20, 819, 21, 81876~89 95, 744, 202, 637, 190, 649, 181, 658, 137, 702, 125, 714, 151,688  90~115 217, 622, 128, 711, 142, 697, 122, 717, 203, 636, 118, 721,110, 729, 89, 750, 103, 736, 61, 778, 55, 784, 15, 824, 14, 825 116~13512, 827, 23, 816, 34, 805, 37, 802, 46, 793, 207, 632, 179, 660, 145,694, 130, 709, 223, 616 136~167 228, 611, 227, 612, 132, 707, 133, 706,143, 696, 135, 704, 161, 678, 201, 638, 173, 666, 106, 733, 83, 756, 91,748, 66, 773, 53, 786, 10, 829, 9, 830 168~203 7, 832, 8, 831, 16, 823,47, 792, 64, 775, 57, 782, 104, 735, 101, 738, 108, 731, 208, 631, 184,655, 197, 642, 191, 648, 121, 718, 141, 698, 149, 690, 216, 623, 218,621 204~263 152, 687, 144, 695, 134, 705, 138, 701, 199, 640, 162, 677,176, 663, 119, 720, 158, 681, 164, 675, 174, 665, 171, 668, 170, 669,87, 752, 169, 670, 88, 751, 107, 732, 81, 758, 82, 757, 100, 739, 98,741, 71, 768, 59, 780, 65, 774, 50, 789, 49, 790, 26, 813, 17, 822, 13,826, 6, 833 264~327 5, 834, 33, 806, 51, 788, 75, 764, 99, 740, 96, 743,97, 742, 166, 673, 172, 667, 175, 664, 187, 652, 163, 676, 185, 654,200, 639, 114, 725, 189, 650, 115, 724, 194, 645, 195, 644, 192, 647,182, 657, 157, 682, 156, 683, 211, 628, 154, 685, 123, 716, 139, 700,212, 627, 153, 686, 213, 626, 215, 624, 150, 689 328~383 225, 614, 224,615, 221, 618, 220, 619, 127, 712, 147, 692, 124, 715, 193, 646, 205,634, 206, 633, 116, 723, 160, 679, 186, 653, 167, 672, 79, 760, 85, 754,77, 762, 92, 747, 58, 781, 62, 777, 69, 770, 54, 785, 36, 803, 32, 807,25, 814, 18, 821, 11, 828,4, 835 384~455 3, 836, 19, 820, 22, 817, 41,798, 38, 801, 44, 795, 52, 787, 45, 794, 63, 776, 67, 772, 72, 767, 76,763, 94, 745, 102, 737, 90, 749, 109, 730, 165, 674, 111, 728, 209, 630,204, 635, 117, 722, 188, 651, 159, 680, 198, 641, 113, 726, 183, 656,180, 659, 177, 662, 196, 643, 155, 684, 214, 625, 126, 713, 131, 708,219, 620, 222, 617, 226, 613 456~513 230, 609, 232, 607, 262, 577, 252,587, 418, 421, 416, 423, 413, 426, 411, 428, 376, 463, 395, 444, 283,556, 285, 554, 379, 460, 390, 449, 363, 476, 384, 455, 388, 451, 386,453, 361, 478, 387, 452, 360, 479, 310, 529, 354, 485, 328, 511, 315,524, 337, 502, 349, 490, 335, 504, 324, 515 514~561 323, 516, 320, 519,334, 505, 359, 480, 295, 544, 385, 454, 292, 547, 291, 548, 381, 458,399, 440, 380, 459, 397, 442, 369, 470, 377, 462, 410, 429, 407, 432,281, 558, 414, 425, 247, 592, 277, 562, 271, 568, 272, 567, 264, 575,259, 580 562~629 237, 602, 239, 600, 244, 595, 243, 596, 275, 564, 278,561, 250, 589, 246, 593, 417, 422, 248, 591, 394, 445, 393, 446, 370,469, 365, 474, 300, 539, 299, 540, 364, 475, 362, 477, 298, 541, 312,527, 313, 526, 314, 525, 353, 486, 352, 487, 343, 496, 327, 512, 350,489, 326, 513, 319, 520, 332, 507, 333, 506, 348, 491, 347, 492, 322,517 630~659 330, 509, 338, 501, 341, 498, 340, 499, 342, 497, 301, 538,366, 473, 401, 438, 371, 468, 408, 431, 375, 464, 249, 590, 269, 570,238, 601, 234, 605 660~707 257, 582, 273, 566, 255, 584, 254, 585, 245,594, 251, 588, 412, 427, 372, 467, 282, 557, 403, 436, 396, 443, 392,447, 391, 448, 382, 457, 389, 450, 294, 545, 297, 542, 311, 528, 344,495, 345, 494, 318, 521, 331, 508, 325, 514, 321, 518 708~729 346, 493,339, 500, 351, 488, 306, 533, 289, 550, 400, 439, 378, 461, 374, 465,415, 424, 270, 569, 241, 598 730~751 231, 608, 260, 579, 268, 571, 276,563, 409, 430, 398, 441, 290, 549, 304, 535, 308, 531, 358, 481, 316,523 752~765 293, 546, 288, 551, 284, 555, 368, 471, 253, 586, 256, 583,263, 576 766~777 242, 597, 274, 565, 402, 437, 383, 456, 357, 482, 329,510 778~789 317, 522, 307, 532, 286, 553, 287, 552, 266, 573, 261, 578790~795 236, 603, 303, 536, 356, 483 796~803 355, 484, 405, 434, 404,435, 406, 433 804~809 235, 604, 267, 572, 302, 537 810~815 309, 530,265, 574, 233, 606 816~819 367, 472, 296, 543 820~837 336, 503, 305,534, 373, 466, 280, 559, 279, 560, 419, 420, 240, 599, 258, 581, 229,610

TABLE 3 Logical root Physical root sequence number u sequence number (inincreasing order of the corresponding logical sequence number)  0-19 1138 2 137 3 136 4 135 5 134 6 133 7 132 8 131 9 130 10 129 20-39 11 12812 127 13 126 14 125 15 124 16 123 17 122 18 121 19 120 20 119 40-59 21118 22 117 23 116 24 115 25 114 26 113 27 112 28 111 29 110 30 109 60-7931 108 32 107 33 106 34 105 35 104 36 103 37 102 38 101 39 100 40 9980-99 41 98 42 97 43 96 44 95 45 94 46 93 47 92 48 91 49 90 50 89100-119 51 88 52 87 53 86 54 85 55 84 56 83 57 82 58 81 59 80 60 79120-137 61 78 62 77 63 76 64 75 65 74 66 73 67 72 68 71 69 70 — —138-837 N/A

u-th root Zadoff-Chu sequence is defined by the following equation.Equation 1

${{x_{u}(n)} = e^{{- j}\frac{\pi\;{{un}{({n + 1})}}}{N_{ZC}}}},{0 \leq n \leq {N_{ZC} - 1}}$

TABLE 4 Preamble format N_(ZC) 0~3 839 4 139

From the u-th root Zadoff-Chu sequence, random access preambles withzero correlation zones of length N_(ZC)−1 are defined by cyclic shiftsaccording to x_(u,v)(n)=x_(u)((n+C_(v)) mod N_(ZC)), where the cyclicshift is given by the following equation.Equation 2

$C_{v} = \left\{ \begin{matrix}{vN}_{CS} & {{v = 0},1,\ldots\mspace{11mu},{\left\lfloor {N_{ZC}/N_{CS}} \right\rfloor - 1},{N_{CS} \neq 0}} & {{for}\mspace{14mu}{unrestricted}\mspace{14mu}{sets}} \\0 & {N_{CS} = 0} & {{for}\mspace{14mu}{unrestricted}\mspace{14mu}{sets}} \\{{d_{start}\left\lfloor {v/n_{shift}^{RA}} \right\rfloor} + {\left( {{v{mod}}\; n_{shift}^{RA}} \right)N_{CS}}} & {{v = 0},1,\ldots\mspace{11mu},{{n_{shift}^{RA}n_{group}^{RA}} + {\overset{\_}{n}}_{shift}^{RA} - 1}} & {{for}\mspace{14mu}{restricted}\mspace{14mu}{sets}}\end{matrix} \right.$

N_(CS) is given by Table 5 for preamble formats 0-3 and by Table 6 forpreamble format 4.

TABLE 5 N_(CS) value zeroCorrelationZoneConfig Unrestricted setRestricted set 0 0 15 1 13 18 2 15 22 3 18 26 4 22 32 5 26 38 6 32 46 738 55 8 46 68 9 59 82 10 76 100 11 93 128 12 119 158 13 167 202 14 279237 15 419 —

TABLE 6 zeroCorrelationZoneConfig N_(CS) value 0  2 1  4 2  6 3  8 4 105 12 6 15 7 N/A 8 N/A 9 N/A 10 N/A 11 N/A 12 N/A 13 N/A 14 N/A 15 N/A

The parameter zeroCorrelationZoneConfig is provided by higher layers.The parameter High-speed-flag provided by higher layers determines ifunrestricted set or restricted set shall be used.

The variable d_(u) is the cyclic shift corresponding to a Doppler shiftof magnitude 1/T_(SEQ) and is given by the following equation.Equation 3

$d_{u} = \left\{ \begin{matrix}p & {0 \leq p < {N_{ZC}/2}} \\{N_{ZC} - p} & {otherwise}\end{matrix} \right.$

p is the smallest non-negative integer that fulfils (pu) mod N_(ZC)=1.The parameters for restricted sets of cyclic shifts depend on d_(u). ForN_(ZC)≤d_(n)<N_(ZC)/3, the parameters are given by the followingequation.n _(shift) ^(RA) =└d _(u) /N _(CS)┘d _(start)=2d _(u) +n _(shift) ^(RA) N _(CS)n _(group) ^(RA) =└N _(ZC) /d _(start)┘n _(shift) ^(RA)=max(└(N _(ZC)−2d _(u) −n _(group) ^(RA) d _(start))/N_(CS)┘,0)   Equation 4

For N_(ZC)/3≤d_(u)<(N_(ZC)−N_(CS))/2, the parameters are given by thefollowing equation.n _(shift) ^(RA)=└(N _(ZC)−2d _(u))/N _(CS)┘d _(start) =N _(ZC)−2d _(u) +n _(shift) ^(RA) N _(CS)n _(group) ^(RA) =└d _(u) /d _(start)┘n _(shift) ^(RA)=min(max(└(d _(u) −n _(group) ^(RA) d _(start))/N_(CS)┘,0),n _(shift) ^(RA))   Equation 5

For all other values of d_(u), there are no cyclic shifts in therestricted set.

The time-continuous random access signal s(t) which is the basebandsignal of RACH is defined by the following Equation.Equation 6

${s(t)} = {\beta_{PRACH}{\sum\limits_{k = 0}^{N_{ZC} - 1}\;{\sum\limits_{n = 0}^{N_{ZC} - 1}\;{{x_{u,v}(n)} \cdot e^{{- j}\frac{2\pi\;{nk}}{N_{ZC}}} \cdot e^{j\; 2{\pi{({k + \varphi + {K{({k_{0} + {1/2}})}}})}}\Delta\;{f_{RA}{({t - T_{CP}})}}}}}}}$

where 0≤t<T_(SEQ)−T_(CP), β_(PRACH) is an amplitude scaling factor inorder to conform to the transmit power specified in 3GPP TS 36.211, andk₀=n^(RA) _(PRB)N^(RB) _(sc)−N^(UL) _(RB)N^(RB) _(sc)/2. N^(RB) _(sc)denotes the number of subcarriers constituting one resource block (RB).N^(UL) _(RB) denotes the number of RBs in a UL slot and depends on a ULtransmission bandwidth. The location in the frequency domain iscontrolled by the parameter n^(RA) _(PRB) is derived from the section5.7.1 of 3GPP TS 36.211. The factor K=Δf/Δf_(RA) accounts for thedifference in subcarrier spacing between the random access preamble anduplink data transmission. The variable Δf_(RA), the subcarrier spacingfor the random access preamble, and the variable φ, a fixed offsetdetermining the frequency-domain location of the random access preamblewithin the physical resource blocks, are both given by the followingtable.

TABLE 7 Preamble format Δf_(RA) φ 0~3 1250 Hz 7 4 7500 Hz 2

In the LTE/LTE-A system, a subcarrier spacing Δf is 15 kHz or 7.5 kHz.However, as given by Table 7, a subcarrier spacing Δf_(RA) for a randomaccess preamble is 1.25 kHz or 0.75 kHz.

As more communication devices have demanded higher communicationcapacity, there has been necessity of enhanced mobile broadband relativeto legacy radio access technology (RAT). In addition, massive machinetype communication for providing various services irrespective of timeand place by connecting a plurality of devices and objects to each otheris one main issue to be considered in future-generation communication.Further, a communication system design in which services/UEs sensitiveto reliability and latency are considered is under discussion. Theintroduction of future-generation RAT has been discussed by taking intoconsideration enhanced mobile broadband communication, massive MTC,ultra-reliable and low-latency communication (URLLC), and the like. Incurrent 3GPP, a study of the future-generation mobile communicationsystem after EPC is being conducted. In the present invention, thecorresponding technology is referred to as a new RAT (NR) or 5G RAT, forconvenience.

An NR communication system demands that much better performance than alegacy fourth generation (4G) system be supported in terms of data rate,capacity, latency, energy consumption, and cost. Accordingly, the NRsystem needs to make progress in terms of bandwidth, spectrum, energy,signaling efficiency, and cost per bit.

<OFDM Numerology>

The new RAT system uses an OFDM transmission scheme or a similartransmission scheme. The new RAT system may follow the OFDM parametersdifferent from OFDM parameters of the LTE system. Alternatively, the newRAT system may conform to numerology of the legacy LTE/LTE-A system butmay have a broader system bandwidth (e.g., 100 MHz) than the legacyLTE/LTE-A system. One cell may support a plurality of numerologies. Thatis, UEs that operate with different numerologies may coexist within onecell.

<Subframe Structure>

In the 3GPP LTE/LTE-A system, radio frame is 10 ms (307,200 T_(s)) induration. The radio frame is divided into 10 subframes of equal size.Subframe numbers may be assigned to the 10 subframes within one radioframe, respectively. Here, T_(s) denotes sampling time whereT_(s)=1/(2048*15 kHz). The basic time unit for LTE is T_(s). Eachsubframe is 1 ms long and is further divided into two slots. 20 slotsare sequentially numbered from 0 to 19 in one radio frame. Duration ofeach slot is 0.5 ms. A time interval in which one subframe istransmitted is defined as a transmission time interval (TTI). Timeresources may be distinguished by a radio frame number (or radio frameindex), a subframe number (or subframe index), a slot number (or slotindex), and the like. The TTI refers to an interval during which datacan be scheduled. For example, in a current LTE/LTE-A system, atransmission opportunity of a UL grant or a DL grant is present every 1ms and several transmission opportunities of the UL/DL grant are notpresent within a shorter time than 1 ms. Therefore, the TTI in thelegacy LTE/LTE-A system is 1 ms.

FIG. 2 illustrates a slot structure available in a new radio accesstechnology (NR).

To minimize data transmission latency, in a 5G new RAT, a slot structurein which a control channel and a data channel aretime-division-multiplexed is considered.

In FIG. 2, the hatched area represents the transmission region of a DLcontrol channel (e.g., PDCCH) carrying the DCI, and the black arearepresents the transmission region of a UL control channel (e.g., PUCCH)carrying the UCI. Here, the DCI is control information that the gNBtransmits to the UE. The DCI may include information on cellconfiguration that the UE should know, DL specific information such asDL scheduling, and UL specific information such as UL grant. The UCI iscontrol information that the UE transmits to the gNB. The UCI mayinclude a HARQ ACK/NACK report on the DL data, a CSI report on the DLchannel status, and a scheduling request (SR).

In FIG. 2, the region of symbols from symbol index 1 to symbol index 12may be used for transmission of a physical channel (e.g., a PDSCH)carrying downlink data, or may be used for transmission of a physicalchannel (e.g., PUSCH) carrying uplink data. According to the slotstructure of FIG. 2, DL transmission and UL transmission may besequentially performed in one slot, and thus transmission/reception ofDL data and reception/transmission of UL ACK/NACK for the DL data may beperformed in one slot. As a result, the time taken to retransmit datawhen a data transmission error occurs may be reduced, thereby minimizingthe latency of final data transmission.

In such a slot structure, a time gap is needed for the process ofswitching from the transmission mode to the reception mode or from thereception mode to the transmission mode of the gNB and UE. On behalf ofthe process of switching between the transmission mode and the receptionmode, some OFDM symbols at the time of switching from DL to UL in theslot structure are set as a guard period (GP).

In the legacy LTE/LTE-A system, a DL control channel istime-division-multiplexed with a data channel and a PDCCH, which is acontrol channel, is transmitted throughout an entire system band.However, in the new RAT, it is expected that a bandwidth of one systemreaches approximately a minimum of 100 MHz and it is difficult todistribute the control channel throughout the entire band fortransmission of the control channel. For data transmission/reception ofa UE, if the entire band is monitored to receive the DL control channel,this may cause increase in battery consumption of the UE anddeterioration in efficiency. Accordingly, in the present invention, theDL control channel may be locally transmitted or distributivelytransmitted in a partial frequency band in a system band, i.e., achannel band.

In the NR system, a basic transmission unit is a slot. A slot durationmay consist of 14 symbols with a normal cyclic prefix (CP) or 12 symbolswith an extended CP. The slot is scaled in time as a function of a usedsubcarrier spacing. That is, if the subcarrier spacing increases, thelength of the slot is shortened. For example, when the number of symbolsper slot is 14, the number of slots in a 10-ms frame is 10 at asubcarrier spacing of 15 kHz, 20 at a subcarrier spacing of 30 kHz, and40 at a subcarrier spacing of 60 kHz. If a subcarrier spacing increases,the length of OFDM symbols is shortened. The number of OFDM symbols in aslot depends on whether the OFDM symbols have a normal CP or an extendedCP and does not vary according to subcarrier spacing. A basic time unitused in the LTE system, T_(s), is defined as T_(s)=1/(15000*2048)seconds in consideration of a basic subcarrier spacing of 15 kHz and amaximum TFT size 2048 of the LTE system and corresponds to a samplingtime for a subcarrier spacing of 15 kHz. In the NR system, varioussubcarrier lengths in addition to the subcarrier spacing of 15 kHz maybe used. Since the subcarrier spacing and a corresponding time lengthare inversely proportional, an actual sampling time corresponding tosubcarrier spacings greater than 15 kHz is shorter thanT_(s)=1/(15000*2048) seconds. For example, actual sampling times forsubcarrier spacings of 30 kHz, 60 kHz, and 120 kHz will be1/(2*15000*2048) seconds, 1/(4*15000*2048) seconds, and 1/(8*15000*2048)seconds, respectively.

<Analog Beamforming>

A recently discussed fifth generation (5G) mobile communication systemis considering using an ultrahigh frequency band, i.e., a millimeterfrequency band equal to or higher than 6 GHz, to transmit data to aplurality of users in a wide frequency band while maintaining a hightransmission rate. In 3GPP, this system is used as NR and, in thepresent invention, this system will be referred to as an NR system.Since the millimeter frequency band uses too high a frequency band, afrequency characteristic thereof exhibits very sharp signal attenuationdepending on distance. Therefore, in order to correct a sharppropagation attenuation characteristic, the NR system using a band of atleast above 6 GHz uses a narrow beam transmission scheme to solve acoverage decrease problem caused by sharp propagation attenuation bytransmitting signals in a specific direction so as to focus energyrather than in all directions. However, if a signal transmission serviceis provided using only one narrow beam, since a range serviced by one BSbecomes narrow, the BS provides a broadband service by gathering aplurality of narrow beams.

In the millimeter frequency band, i.e., millimeter wave (mmW) band, thewavelength is shortened, and thus a plurality of antenna elements may beinstalled in the same area. For example, a total of 100 antenna elementsmay be installed in a 5-by-5 cm panel in a 30 GHz band with a wavelengthof about 1 cm in a 2-dimensional array at intervals of 0.5λ(wavelength). Therefore, in mmW, increasing the coverage or thethroughput by increasing the beamforming (BF) gain using multipleantenna elements is taken into consideration.

As a method of forming a narrow beam in the millimeter frequency band, abeamforming scheme is mainly considered in which the BS or the UEtransmits the same signal using a proper phase difference through alarge number of antennas so that energy increases only in a specificdirection. Such a beamforming scheme includes digital beamforming forimparting a phase difference to a digital baseband signal, analogbeamforming for imparting a phase difference to a modulated analogsignal using time latency (i.e., cyclic shift), and hybrid beamformingusing both digital beamforming and analog beamforming. If a transceiverunit (TXRU) is provided for each antenna element to enable adjustment oftransmit power and phase, independent beamforming is possible for eachfrequency resource. However, installing TXRU in all of the about 100antenna elements is less feasible in terms of cost. That is, themillimeter frequency band needs to use numerous antennas to correct thesharp propagation attenuation characteristic. Digital beamformingrequires as many radio frequency (RF) components (e.g., adigital-to-analog converter (DAC), a mixer, a power amplifier, a linearamplifier, etc.) as the number of antennas. Therefore, if digitalbeamforming is desired to be implemented in the millimeter frequencyband, cost of communication devices increases. Hence, when a largenumber of antennas is needed as in the millimeter frequency band, use ofanalog beamforming or hybrid beamforming is considered. In the analogbeamforming method, multiple antenna elements are mapped to one TXRU anda beam direction is adjusted using an analog phase shifter. This analogbeamforming method may only make one beam direction in the whole band,and thus may not perform frequency selective beamforming (BF), which isdisadvantageous. The hybrid BF method is an intermediate type of digitalBF and analog BF and uses B TXRUs less in number than Q antennaelements. In the case of hybrid BF, the number of directions in whichbeams may be transmitted at the same time is limited to B or less, whichdepends on the method of collection of B TXRUs and Q antenna elements.

As mentioned above, digital BF may simultaneously transmit or receivesignals in multiple directions using multiple beams by processing adigital baseband signal to be transmitted or received, whereas analog BFcannot simultaneously transmit or receive signals in multiple directionsexceeding a coverage range of one beam by performing BF in a state inwhich an analog signal to be transmitted or received is modulated.Typically, the BS simultaneously performs communication with a pluralityof users using broadband transmission or multi-antenna characteristics.If the BS uses analog or hybrid BF and forms an analog beam in one beamdirection, the eNB communicates with only users included in the sameanalog beam direction due to an analog BF characteristic. A RACHresource allocation method and a resource use method of the BS accordingto the present invention, which will be described later, are proposedconsidering restrictions caused by the analog BF or hybrid BFcharacteristic.

<Hybrid Analog Beamforming>

FIG. 3 abstractly illustrates TXRUs and a hybrid BF structure in termsof physical antennas.

When a plurality of antennas is used, a hybrid BF method in whichdigital BF and analog BF are combined is considered. Analog BF (or RFBF) refers to an operation in which an RF unit performs precoding (orcombining). In hybrid BF, each of a baseband unit and the RF unit (alsoreferred to as a transceiver) performs precoding (or combining) so thatperformance approximating to digital BF can be obtained while the numberof RF chains and the number of digital-to-analog (D/A) (oranalog-to-digital (A/D)) converters is reduced. For convenience, thehybrid BF structure may be expressed as N TXRUs and M physical antennas.Digital BF for L data layers to be transmitted by a transmitter may beexpressed as an N-by-L matrix. Next, N converted digital signals areconverted into analog signals through the TXRUs and analog BF expressedas an M-by-N matrix is applied to the analog signals. In FIG. 3, thenumber of digital beams is L and the number of analog beams is N. In theNR system, the BS is designed so as to change analog BF in units ofsymbols and efficient BF support for a UE located in a specific regionis considered. If the N TXRUs and the M RF antennas are defined as oneantenna panel, the NR system considers even a method of introducingplural antenna panels to which independent hybrid BF is applicable. Inthis way, when the BS uses a plurality of analog beams, since whichanalog beam is favorable for signal reception may differ according toeach UE, a beam sweeping operation is considered so that, for at least asynchronization signal, system information, and paging, all UEs may havereception opportunities by changing a plurality of analog beams, thatthe BS is to apply, according to symbols in a specific slot or subframe.

Recently, a 3GPP standardization organization is considering networkslicing to achieve a plurality of logical networks in a single physicalnetwork in a new RAT system, i.e., the NR system, which is a 5G wirelesscommunication system. The logical networks should be capable ofsupporting various services (e.g., eMBB, mMTC, URLLC, etc.) havingvarious requirements. A physical layer system of the NR system considersa method supporting an orthogonal frequency division multiplexing (OFDM)scheme using variable numerologies according to various services. Inother words, the NR system may consider the OFDM scheme (or multipleaccess scheme) using independent numerologies in respective time andfrequency resource regions.

Recently, as data traffic remarkably increases with appearance ofsmartphone devices, the NR system needs to support of highercommunication capacity (e.g., data throughput). One method considered toraise the communication capacity is to transmit data using a pluralityof transmission (or reception) antennas. If digital BF is desired to beapplied to the multiple antennas, each antenna requires an RF chain(e.g., a chain consisting of RF elements such as a power amplifier and adown converter) and a D/A or A/D converter. This structure increaseshardware complexity and consumes high power which may not be practical.Accordingly, when multiple antennas are used, the NR system considersthe above-mentioned hybrid BF method in which digital BF and analog BFare combined.

FIG. 4 illustrates a cell of a new radio access technology (NR) system.

Referring to FIG. 4, in the NR system, a method in which a plurality oftransmission and reception points (TRPs) form one cell is beingdiscussed unlike a wireless communication system of legacy LTE in whichone BS forms one cell. If the plural TRPs form one cell, seamlesscommunication can be provided even when a TRP that provides a service toa UE is changed so that mobility management of the UE is facilitated.

In an LTE/LTE-A system, a PSS/SSS is transmitted omni-directionally.Meanwhile, a method is considered in which a gNB which uses millimeterwave (mmWave) transmits a signal such as a PSS/SSS/PBCH through BF whilesweeping beam directions omni-directionally. Transmission/reception of asignal while sweeping beam directions is referred to as beam sweeping orbeam scanning. In the present invention, “beam sweeping” represents abehavior of a transmitter and “beam scanning” represents a behavior of areceiver. For example, assuming that the gNB may have a maximum of Nbeam directions, the gNB transmits a signal such as a PSS/SSS/PBCH ineach of the N beam directions. That is, the gNB transmits asynchronization signal such as the PSS/SSS/PBCH in each direction whilesweeping directions that the gNB can have or the gNB desires to support.Alternatively, when the gNB can form N beams, one beam group may beconfigured by grouping a few beams and the PSS/SSS/PBCH may betransmitted/received with respect to each beam group. In this case, onebeam group includes one or more beams. The signal such as thePSS/SSS/PBCH transmitted in the same direction may be defined as onesynchronization (SS) block and a plurality of SS blocks may be presentin one cell. When the plural SS blocks are present, SS block indexes maybe used to distinguish between the SS blocks. For example, if thePSS/SSS/PBCH is transmitted in 10 beam directions in one system, thePSS/SSS/PBCH transmitted in the same direction may constitute one SSblock and it may be understood that 10 SS blocks are present in thesystem. In the present invention, a beam index may be interpreted as anSS block index.

FIG. 5 illustrates transmission of an SS block and a RACH resourcelinked to the SS block.

To communicate with one UE, the gNB should acquire an optimal beamdirection between the gNB and the UE and should continuously track theoptimal beam direction because the optimal beam direction is changed asthe UE moves. A procedure of acquiring the optimal beam directionbetween the gNB and the UE is referred to as a beam acquisitionprocedure and a procedure of continuously tracking the optimal beamdirection is referred to as a beam tracking procedure. The beamacquisition procedure is needed for 1) initial access in which the UEfirst attempts to access the gNB, 2) handover in which the UE is handedover from one gNB to another gNB, or 3) beam recovery for recoveringfrom a state in which the UE and gNB cannot maintain an optimalcommunication state or enter a communication impossible state, i.e.,beam failure, as a result of losing an optimal beam while performingbeam tracking for searching for the optimal beam between the UE and thegNB.

In the case of the NR system which is under development, a multi-stagebeam acquisition procedure is under discussion, for beam acquisition inan environment using multiple beams. In the multi-stage beam acquisitionprocedure, the gNB and the UE perform connection setup using a wide beamin an initial access stage and, after connection setup is ended, the gNBand the UE perform communication with optimal quality using a narrowband. In the present invention, although various methods for beamacquisition of the NR system are mainly discussed, the most activelydiscussed method at present is as follows.

1) The gNB transmits an SS block per wide beam in order for the UE tosearch for the gNB in an initial access procedure, i.e., performs cellsearch or cell acquisition, and to search for an optimal wide beam to beused in a first stage of beam acquisition by measuring channel qualityof each wide beam. 2) The UE performs cell search for an SS block perbeam and performs DL beam acquisition using a cell detection result ofeach beam. 3) The UE performs a RACH procedure in order to inform thegNB that the UE will access the gNB that the UE has discovered. 4) ThegNB connects or associates the SS block transmitted per beam and a RACHresource to be used for RACH transmission, in order to cause the UE toinform the gNB of a result of the RACH procedure and simultaneously aresult of DL beam acquisition (e.g., beam index) at a wide beam level.If the UE performs the RACH procedure using a RACH resource connected toan optimal beam direction that the UE has discovered, the gNB obtainsinformation about a DL beam suitable for the UE in a procedure ofreceiving a RACH preamble.

<Beam Correspondence (BC)>

In a multi-beam environment, whether a UE and/or a TRP can accuratelydetermine a transmission (Tx) or reception (Rx) beam direction betweenthe UE and the TRP is problematic. In the multi-beam environment, signaltransmission repetition or beam sweeping for signal reception may beconsidered according to a Tx/Rx reciprocal capability of the TRP (e.g.,eNB) or the UE. The Tx/Rx reciprocal capability is also referred to asTx/Rx beam correspondence (BC) in the TRP and the UE. In the multi-beamenvironment, if the Tx/Rx reciprocal capability in the TRP or the UEdoes not hold, the UE may not transmit a UL signal in a beam directionin which the UE has received a DL signal because an optimal path of ULmay be different from an optimal path of DL. Tx/Rx BC in the TRP holds,if the TRP can determine a TRP Rx beam for UL reception based on DLmeasurement of UE for one or more Tx beams of the TRP and/or if the TRPcan determine a TRP Tx beam for DL transmission based on UL measurementfor one or more Rx beams of the TRP. Tx/Rx BC in the UE holds if the UEcan determine a UE Rx beam for UL transmission based on DL measurementof UE for one or more Rx beams of the UE and/or if the UE can determinea UE Tx beam for DL reception according to indication of the TRP basedon UL measurement for one or more Tx beams of the UE.

In the LTE system and the NR system, a RACH signal used for initialaccess to the gNB, i.e., initial access to the gNB through a cell usedby the gNB, may be configured using the following elements.

Cyclic prefix (CP): This element serves to prevent interferencegenerated from a previous/front (OFDM) symbol and group RACH preamblesignals arriving at the gNB with various time delays into one time zone.That is, if the CP is configured to match a maximum radius of a cell,RACH preambles that UEs in the cell have transmitted in the sameresource are included in a RACH reception window corresponding to thelength of RACH preambles configured by the gNB for RACH reception. A CPlength is generally set to be equal to or greater than a maximum roundtrip delay.

Preamble: A sequence used by the gNB to detect signal transmission isdefined and the preamble serves to carry this sequence.

Guard time (GT): This element is defined to cause a RACH signal arrivingat the gNB with delay from the farthest distance from the gNB on RACHcoverage not to create interference with respect to a signal arrivingafter a RACH symbol duration. During this GT, the UE does not transmit asignal so that the GT may not be defined as the RACH signal.

FIG. 6 illustrates configuration/format of a RACH preamble and areceiver function.

The UE transmits a RACH signal through a designated RACH resource at asystem timing of the gNB obtained through an SS. The gNB receivessignals from multiple UEs. Generally, the gNB performs the procedureillustrated in FIG. 5 for RACH signal reception. Since a CP for the RACHsignal is set to a maximum round trip delay or more, the gNB mayconfigure an arbitrary point between the maximum round trip delay andthe CP length as a boundary for signal reception. If the boundary isdetermined as a start point for signal reception and if correlation isapplied to a signal of a length corresponding to a sequence length fromthe start point, the gNB may acquire information as to whether the RACHsignal is present and information about the CP.

If a communication environment operated by the gNB such as a millimeterband uses multiple beams, the RACH signal arrives at the eNB frommultiple directions and the gNB needs to detect the RACH preamble (i.e.,PRACH) while sweeping beam directions to receive the RACH signalarriving from multiple directions. As mentioned above, when analog BF isused, the gNB performs RACH reception only in one direction at onetiming. For this reason, it is necessary to design the RACH preamble anda RACH procedure so that the gNB may properly detect the RACH preamble.The present invention proposes the RACH preamble and/or the RACHprocedure for a high frequency band to which the NR system, especially,BF, is applicable in consideration of the case in which BC of the gNBholds and the case in which BC does not hold.

FIG. 7 illustrates a reception (Rx) beam formed at a gNB to receive aRACH preamble.

If BC does not hold, beam directions may be mismatched even when the gNBforms an Rx beam in a Tx beam direction of an SS block in a state inwhich a RACH resource is linked to the SS block. Therefore, a RACHpreamble may be configured in a format illustrated in FIG. 7(a) so thatthe gNB may perform beam scanning for performing/attempting to performRACH preamble detection in multiple directions while sweeping Rx beams.Meanwhile, if BC holds, since the RACH resource is linked to the SSblock, the gNB may form an Rx beam in a direction used to transmit theSS block with respect to one RACH resource and detect the RACH preambleonly in that direction. Therefore, the RACH preamble may be configuredin a format illustrated in FIG. 7(b).

As described previously, a RACH signal and a RACH resource should beconfigured in consideration of two purposes of a DL beam acquisitionreport and a DL preferred beam report of the UE and beam scanning of thegNB according to BC.

FIG. 8 illustrates a RACH signal and a RACH resource to explain termsused to describe the present invention. In the present invention, theRACH signal may be configured as follows.

-   -   RACH resource element: The RACH resource element is a basic unit        used when the UE transmits the RACH signal. Since different RACH        resource elements may be used for RACH signal transmission by        different UEs, respectively, a CP is inserted into the RACH        signal in each RACH resource element. Protection for signals        between UEs is already maintained by the CP and, therefore, a GT        is not needed between RACH resource elements.    -   RACH resource: The RACH resource is defined as a set of        concatenated RACH resource elements connected to one SS block.        If RACH resources are consecutively allocated contiguously, two        successive RACH resources may be used for signal transmission by        different UEs, respectively, like the RACH resource elements.        Therefore, the CP may be inserted into the RACH signal in each        RACH resource. The GT is unnecessary between RACH resources        because signal detection distortion caused by time delay is        prevented by the CP. However, if only one RACH resource is        configured, i.e., RACH resources are not consecutively        configured, since a PUSCH/PUCCH may be allocated after the RACH        resource, the GT may be inserted in front of the PUSCH/PUCCH.    -   RACH resource set: The RACH resource set is a set of        concatenated RACH resources. If multiple SS blocks are present        in a cell and RACH resources connected respectively to the        multiple SS blocks are concatenated, the concatenated RACH        resources may be defined as one RACH resource set. The GT is        inserted into the last of the RACH resource set which is a part        where the RACH resource set including RACH resources and another        signal such as a PUSCH/PUCCH may be encountered. As mentioned        above, since the GT is a duration during which a signal is not        transmitted, the GT may not be defined as a signal. The GT is        not illustrated in FIG. 8.    -   RACH preamble repetition: When a RACH preamble for Rx beam        scanning of the gNB is configured, i.e., when the gNB configures        a RACH preamble format so that the gNB may perform Rx beam        scanning, if the same signal (i.e., same sequence) is repeated        within the RACH preamble, the CP is not needed between the        repeated signals because the repeated signals serve as the CP.        However, when preambles are repeated within the RACH preamble        using different signals, the CP is needed between the preambles.        The GT is not needed between RACH preambles. Hereinafter, the        present invention is described under the assumption that the        same signal is repeated. For example, if the RACH preamble is        configured in the form of ‘CP+preamble+preamble’, the present        invention is described under the assumption that the preambles        within the RACH preamble are configured by the same sequence.

FIG. 8 illustrates RACH resources for a plurality of SS blocks and RACHpreambles in each RACH resource in terms of the gNB. The gNB attempts toreceive a RACH preamble in each RACH resource in a time region in whichthe RACH resources are configured. The UE transmits a RACH preamblethereof through RACH resource(s) linked to specific SS block(s) (e.g.,SS block(s) having better Rx quality) rather than transmitting the RACHpreamble in each of RACH resources for all SS blocks of the cell. Asmentioned above, different RACH resource elements or different RACHresources may be used to transmit RACH preambles by different UEs.

FIG. 9 illustrates a RACH resource set. FIG. 9(a) illustrates the casein which two RACH resource elements per RACH resource are configured ina cell of the gNB in which BC holds. FIG. 9(b) illustrates the case inwhich one RACH resource element per RACH resource is configured in thecell of the gNB in which BC holds. Referring to FIG. 9(a), two RACHpreambles may be transmitted in a RACH resource linked to an SS block.Referring to FIG. 9(b), one RACH preamble may be transmitted in a RACHresource linked to an SS block.

A RACH resource set may be configured as illustrated in FIG. 9 so as tomaximize the efficiency of a RACH resource using the RACH signalconfiguration characteristic described in FIG. 8. As illustrated in FIG.9, in order to raise use/allocation efficiency of the RACH resource,RACH resources or RACH resource elements may be configured to becompletely concatenated without allocating a blank duration between RACHresources in the RACH resource set.

However, if RACH resources are configured as illustrated in FIG. 9, thefollowing problems may arise. 1) When BC holds and the gNB receives aRACH resource corresponding to SS block # N by forming a beam in thedirection of SS block # N, since an Rx beam is changed at a middle ofOFDM symbols (OSs) defined for a data or control channel, the gNB onlypartially uses resources other than a frequency resource allocated asthe RACH resource. That is, as illustrated in FIG. 9(a), if the gNBforms an Rx beam to receive SS block #1, OS #4 cannot be used for thedata channel or the control channel. 2) When BC does not hold and thegNB performs Rx beam scanning within a RACH resource element, the gNBmay perform RACH preamble detection while receiving a data/controlsignal by forming an Rx beam on each of OSs at a boundary of OS #1/OS#2/OS #3 with respect to a RACH resource corresponding to SS block #1.However, when the gNB performs beam scanning for a RACH resourcecorresponding to SS block #2, a beam direction for receiving thedata/control signal and a beam direction for receiving a RACH preambleare not matched in a duration corresponding to OS #4 so that a problemoccurs in detecting the RACH preamble.

In summary, if the gNB performs beam scanning while changing thedirection of an Rx beam for RACH signal reception and a timing at whichthe Rx beam is changed mismatches an OFDM symbol boundary defined forthe data or control channel, there is a problem of lowering resourceuse/allocation efficiency of the data or control channel serviced in afrequency region other than a frequency resource allocated as the RACHresource. To solve this problem, the present invention proposesallocating a RACH resource as a structure aligned with an OFDM symbolboundary, in order for the gNB to perform RACH preamble detection whilechanging a beam direction in a multi-beam scenario and simultaneouslyfor the gNB to use all radio resources other than the RACH resource forthe data and control channels. When BC holds, by way of example, a RACHresource or a RACH preamble transmitted through the RACH resource may bealigned with an OFDM symbol boundary using two methods as illustrated inFIG. 10.

FIG. 10 illustrates boundary alignment of a RACH resource according tothe present invention. An example illustrated in FIG. 10 corresponds tothe case in which BS holds and two RACH resource elements can betransmitted on one RACH resource. When BC does not hold, one RACHpreamble may be configured by one CP and a plurality of consecutivepreambles as illustrated in FIG. 7(a) or FIG. 8(a). Even in this case,the present invention is applicable. Only one RACH resource element maybe transmitted on one RACH resource and the present invention isapplicable thereto.

1) One (hereinafter, Method 1) of methods for aligning an OFDM symbolboundary and a RACH resource boundary determines a CP length and apreamble length of a RACH preamble by taking into consideration RACHpreamble detection capability by the gNB, coverage of the gNB, and asubcarrier spacing of the RACH preamble and then configure an RACHresource element using the CP length and the preamble length, asillustrated in FIG. 10(a). The gNB may configure the RACH resource bydetermining the number of RACH resource elements per RACH resource inconsideration of the capacity of the RACH resource. The gNB configuresRACH resource(s) such that a boundary of each of RACH resources whichare to be consecutively used is aligned with a boundary of OFDMsymbol(s) which are to be used for the data and control channels. Inthis case, a blank duration may occur between RACH resources. The blankduration may be configured as a duration during which no signals aretransmitted. Alternatively, a signal may be additionally transmitted asa post-fix only to the last RACH resource element in the RACH resource.That is, the UE that transmits a RACH preamble using the last RACHresource element in the time domain among RACH resource elements in aRACH resource may add a post-fix signal to the RACH preamble thereof andthen transmit the RACH preamble. The UE that transmits a RACH preambleusing a RACH resource element other than the last RACH resource elementmay transmit the RACH preamble without adding the post-fix signal.

2) Another method (hereinafter, Method 2) among the methods of aligningthe OFDM symbol boundary and the RACH resource boundary configures a CPlength and a preamble length in order to align the RACH resourceboundary with the OFDM symbol boundary as illustrated in FIG. 10(b).However, since the number of RACH resource elements in each RACHresource may vary, if the length of the RACH preamble is changed tomatch the OFDM symbol boundary, there is a danger of changingcharacteristics of a preamble sequence in the RACH preamble. That is,the length of a Zadoff-Chu (ZC) sequence used to generate a preamble isdetermined as 839 or 130 according to a preamble format as illustratedin Table 4. If the length of the preamble is changed in order to alignthe length of the RACH preamble with the OFDM symbol boundary, thecharacteristics of the ZC sequence which is the preamble sequence mayvary. Therefore, if a RACH preamble format is determined and RACHresource elements per RACH resource are determined, the length of theRACH preamble may be fixed but a CP length may become greater than alength determined in configuring the RACH preamble format so that theRACH resource is aligned with the OFDM symbol boundary. That is, thismethod serves to align a RACH resource boundary, i.e., a RACH preambleboundary transmitted through the RACH resource with an OFDM symbol usedto transmit the data/control channel (i.e., normal OFDM symbol) byfixing the length of each preamble in the RACH preamble and increasingthe CP length to match the OFDM symbol boundary so as to maintaincharacteristics of the preamble sequence. In this case, only CP lengthsof some RACH resource elements may be configured to be increased (i.e.,only CP lengths of some RACH preambles are configured to be increased)or CP lengths of all RACH resource elements may be configured to beproperly increased (i.e., a CP length of each RACH preamble isconfigured to be properly increased). For example, if the gNB configuresthe RACH resource in the time domain configured by OFDM symbols, the gNBconfigures a preamble format indicating a CP length and a sequence partlength such that the sequence part length is a multiple of a positiveinteger of a preamble length obtained from a specific length (e.g., thelength of a ZC sequence for a RACH) according to the number of preamblesto be included in a corresponding RACH preamble and the CP length isequal to a value obtained by subtracting the sequence part length from atotal length of the normal OFDM symbols. If the lengths of OFDM symbolsare all the same, the RACH preamble format according to the presentinvention will be defined such that the sum of a multiple of a positiveinteger of a predefined preamble length (e.g., a preamble lengthobtained from a predefined length of a ZC sequence) and a CP length is amultiple of an OFDM symbol length. When the UE detects an SS block of acell and generates a RACH preamble to be transmitted on a RACH resourceconnected to the SS block, the UE generates the RACH preamble bygenerating each preamble to be included in the RACH preamble using asequence of a specific length (e.g., ZC sequence) according to apreamble format configured by the gNB and adding a CP to a front part ofthe preamble or repetition(s) of the preamble.

Method 1 and Method 2 may be equally applied even when the gNB performsRx beam scanning because BC does not hold. When BC holds for Method 1and Method 2, there is a high possibility that a RACH preamble isconfigured in a format including one preamble. Meanwhile, except thatthere is a high possibility that the RACH preamble is configured toinclude preamble repetition when BC does not hold, Method 1 and Method 2described with reference to FIG. 10 may be equally applied to the casein which the gNB desires to perform Rx beam scanning because BS does nothold. For example, when BC does not hold so that the gNB desires toperform Rx beam scanning, the gNB configures and signals a preambleformat (e.g., refer to FIG. 7(a) or FIG. 8(a)) in the form of includingpreamble repetition. Herein, the RACH resource may be configured in theform of Method 1 so as to monitor RACH preamble(s) by considering aduration from the end of one RACH resource to a part immediately beforethe start of the next RACH resource as a blank duration or a post-fixduration. Alternatively, the RACH resource may be configured in the formof Method 2 so as to monitor RACH preamble(s) in each RACH resourceconfigured by the gNB under the assumption that the RACH preambleboundary is equal to the OFDM symbol boundary.

The RACH resource allocation method proposed in the present inventionserves to efficiently use a frequency resource, other than a frequencyresource occupied by the RACH resource, in one slot or multiple slotsused for the RACH resource, as a data resource or a control channelresource. Therefore, for efficient use of the data/control channelresource considering the RACH resource, the gNB needs to schedule thedata or control channel using information as to which unit is used toform a beam with respect to a slot to which the RACH resource isallocated. The UE may receive information as to which OFDM symbol unitis used when the gNB performs scheduling and transmit the data orcontrol channel based on the information. To this end, two methods maybe considered so that the gNB may schedule the data or control channelin a time region to which the RACH resource is allocated.

Mini Slot Allocation

When a channel is scheduled in a time region to which the RACH resourceis allocated, since the scheduled channel should be included in one beamregion, a time length of a resource to which the channel is allocatedshould be shorter than a time length of the RACH resource and aplurality of slots of a short length may be included for one RACHresource.

If the gNB operates by configuring a beam direction for each RACHresource and time units in which the gNB allocates a resource to the UEare not matched in a time region to which the RACH resource is allocatedand in a time region to which the RACH resource is not allocated, thegNB should define a slot for scheduling in a time region occupied by theRACH resource and inform the UE of information related to the slot.Hereinafter, the slot used for scheduling in the time region occupied bythe RACH resource will be referred to as a mini slot. In this structure,there are some considerations in order to transmit the data or controlchannel through the mini slot. For example, the following considerationsare given.

1) The case in which one mini slot is defined for a slot to which theRACH resource is allocated:

FIG. 11 illustrates a method of configuring a mini slot within a RACHslot SLOT_(RACH) when BC holds.

The UE is aware of all information about RACH resources that the gNBuses through system information. Therefore, a set of minimum OFDMsymbols including a whole RACH resource allocated per SS block may bedefined as one mini slot. When the gNB performs scheduling at a time towhich the RACH resource is allocated, the UE interprets the mini slot asa TTI and transmits the data or control channel in the TTI. If multiplemini slots are included in one normal slot, the UE needs to determinethrough which mini slot the UE is to transmit the data/control channel.A method for the UE to determine a mini slot to be used to transmit thedata/control channel may broadly include the following two schemes.

-   -   A. If the gNB schedules transmission of a UL data/control        channel, the gNB may designate, for the UE, which mini slot        within a slot the UE should use for transmission, through DCI.    -   B. The UE continuously performs beam tracking in a multi-beam        scenario. If the UE previously receives, from the gNB,        information about an SS block to which a serving beam from which        the UE currently receives a service is connected, the UE        interprets the same time region as a time region to which the        RACH resource connected to the SS block associated with the        serving beam is allocated as a time region in which the UE        should perform transmission. If the RACH resource connected to        the SS block associated with the serving beam of the UE is not        present in a slot scheduled for the UE, the UE may determine        that beam mismatch has occurred.

2) The case in which multiple mini slots are defined in a slot to whichthe RACH resource is allocated:

FIG. 12 illustrates another method of configuring a mini slot within aRACH slot SLOT_(RACH) when BC holds.

When multiple mini slots are defined in a slot to which a RACH resourceis allocated, this is basically similar to the case in which multiplemini slots are defined in a slot to which a RACH resource is allocatedexcept that multiple mini slots are present in a slot to which one RACHresource is allocated. The same operation as the method proposed in FIG.11 is performed. However, as illustrated in FIG. 12, a set of minimumOFDM symbols including a whole RACH resource is divided into a fewsubsets and each subset is defined as a mini slot. In this case, the gNBshould first inform the UE of how the set of minimum OFDM symbolsincluding a RACH resource should be divided to use the mini slots. Forexample, the gNB may indicate, in a bitmap form, how the minimum OFDMsymbols including the RACH resource are divided to the UE.Alternatively, when the minimum OFDM symbols including the RACH resourcecan be divided into a plurality of equal subsets, the gNB may inform theUE of the number of allocated mini slots. In addition, the gNB shouldindicate, to the scheduled UE, through which mini slot among themultiple mini slots the UE should transmit the data/control channel. ThegNB may directly indicate a mini slot through which the data/controlchannel should be transmitted through the DCI. Alternatively, when theUE is scheduled in a time region to which the RACH resource isallocated, the gNB may inform the UE of a mini slot to be used, inadvance (e.g., during connection setup). Alternatively, it is possibleto determine a mini slot to be used by a predetermined rule usinginformation, such as a UE ID, which is shared between the UE and thegNB.

3) The case in which BC does not hold and, thus, beam scanning isperformed during preamble repetition:

FIG. 13 illustrates a method of configuring a mini slot within a RACHslot SLOT_(RACH) when BC does not hold.

When BC does not hold, the gNB performs beam scanning while sweepingbeam directions of a receiver in a slot to which one RACH resource isallocated, as described above. Therefore, this case may operatesimilarly to a scheme in which BC holds and multiple mini slots arepresent in a slot to which the RACH resource is allocated. To this end,similarly to the method described in FIG. 12, the gNB transmits, to theUE, information as to how beam scanning will be performed with respectto a set of minimum OFDM symbols including the RACH resource andinformation as to which SS block each beam is connected. Thisinformation may be used as information about which mini slot can bescheduled for the UE. In this case, similarly to the method described inFIG. 12, the UE may receive, through the DCI, the information aboutwhich mini slot among the multiple mini slots which can be scheduled forthe UE is scheduled to transmit the data/control channel. Alternatively,the information may be prescheduled through an RRC signal or may bedefined by a predefined rule using information shared between the gNBand the UE.

4) The Case of Grant-Free Scheduling:

-   -   A. When a time resource of a data/control channel transmitted by        the UE on a grant-free resource overlaps a RACH resource, the        data/control channel may be transmitted in a mini slot defined        in a time region of the RACH resource. However, when grant-free        scheduling is used and a signal format of the data/control        channel that the UE is to transmit through the grant-free        scheduling, i.e., through a grant-free resource, is a normal        slot or a slot which is shorter than the normal slot but is        longer than the mini slot defined in a RACH resource region and        when the length of the mini slot is too short, so that a code        rate of transmission of the data/control channel through the        mini slot is too high relative to a designate code rate, the UE        may i) drop transmission, ii) change a transport block size,        or iii) transmit the data/control channel using multiple mini        slots when the multiple mini slots are available. On the other        hand, when the code rate of transmission of the data/control        channel is lower than the designated code rate even if the        data/control channel is transmitted with the length of the mini        slot, the UE may transmit the data/control channel with a        designated transport block size.    -   B. When grant-free scheduling is used and the signal format of        the data/control channel that the UE is to transmit through the        grant-free scheduling, i.e., through the grant-free resource, is        shorter than the mini slot, the data/control channel may be        normally transmitted at a mini slot location determined in the        above-mentioned scheme. That is, if the data/control channel        through grant-free scheduling requires a resource of a shorter        length than the mini slot in the time domain, the UE transmits        the data/control channel through a mini slot corresponding to        the same gNB Rx beam as the data/control channel among mini        slots configured to match the length of the RACH resource (i.e.,        RACH preamble). In this case, the transport block size may        increase according to a predetermined rule in proportion to a        mini slot length compared with a preconfigured signal format.        For example, if the signal format in which the data/control        channel is transmitted through grant-free scheduling is defined        as using two OFDM symbols and the mini slot length in a RACH        slot corresponds to three OFDM symbols, the transport block size        capable of carrying the data/control channel of grant-free        scheduling may increase by 1.5 times.

5) Allocation of Mini Slot to Guard Time or Blank Duration:

FIG. 14 illustrates a method of configuring a mini slot using a guardtime.

The gNB may freely configure an Rx beam with respect to a part of aduration configured as the guard time, or a blank duration in a slotremaining after configuring a RACH resource in one slot even though theblank duration is not for usage of the guard time. Accordingly, the gNBmay inform the UE of information about a mini slot capable of being usedindependently of a beam for RACH resource reception together withinformation related to the RACH resource and the UE may expect thatdynamic scheduling will be performed with respect to the mini slotconfigured in the guard time. The location(s) of allocated mini slot(s)may be determined by the above-described methods (e.g., methods ofindicating the length and locations of mini slots configured in a RACHslot and a beam direction).

6) Allocation of Short PUCCH Resource:

In a TDD system, a control channel may be transmitted during a partialduration of one slot by configuring the control channel with a shortlength. In an NR system, schemes in which a DL control channel istransmitted in a front part of one slot and a UL control channel istransmitted in the last part of one slot are under discussion.Particularly, the UL control channel transmitted in this way is referredto as a short PUCHH. Since the short PUCCH is configured to betransmitted on the last one or two symbols, the short PUCCH may betransmitted in the above-described mini slot. However, as mentionedpreviously, since a beam direction may vary within one slot, the shortPUCCH cannot always be located at the last part of the slot.Accordingly, when the short PUCCH is scheduled in a slot region to whicha RACH resource is allocated, the UE transmits the short PUCCH in a minislot in which a beam in the same direction as a beam from which the UEreceives a service (i.e., a gNB Rx beam, or a UE Tx beam correspondingto the gNB Rx beam) or a beam in which the gNB previously forms a linkfor the short PUCCH (i.e., a gNB Rx beam, or a UE Tx beam correspondingto the gNB Rx beam) is present. In this case, the PUCCH may betransmitted at the last symbol location in the mini slot, a symbollocation designated by the gNB through signaling, or a symbol locationdetermined by a rule. However, the UE may drop transmission of the shortPUCCH when the beam in the same direction as a beam from which the UEreceives a service or the beam in which the gNB previously forms a linkfor the short PUCCH is not present.

Mini Slot Concatenation

In the procedure of forming the Rx beam for the RACH resource set, if Rxbeam directions of respective RACH resources are not greatly different,the data or control channel may be transmitted through a long slot forperforming transmission throughout a duration of the RACH resource set.This may be referred to as mini slot concatenation in which theabove-described mini slots are used through concatenation as describedabove.

FIG. 15 illustrates an example of transmitting data by performing minislot concatenation with the same length as a normal slot when BC holds.Particularly, FIG. 15 illustrates transmission of concatenated minislots and insertion of a reference signal during a RACH resourceduration when BC holds. For example, one data packet may be transmittedthroughout a long slot obtained by concatenating mini slots so that thelong slot may have the same length as a normal slot. In this case, onedata packet is dividedly transmitted in mini slots within the long slot.

Thus, in the case of data transmission using the concatenated minislots, since the gNB forms an Rx beam of each RACH resource usinginformation about an SS block transmission direction, the UE desirablytransmits a signal in a direction capable of receiving each SS blockwith the best quality. Therefore, the gNB informs the UE of informationrelated to Rx beam formation (e.g., information associated with the SSblock) with respect to each OFDM symbol (when BC does not hold) or withrespect to each RACH resource (when BC holds) in a RACH resource timeregion. In this case, smooth reception of the data channel may not beperformed because the Rx beam of the gNB is changed during signaltransmission while the UE performs signal transmission throughconcatenated mini slots and transmits a reference signal in a formatdefined for a normal slot. Therefore, it is necessary to insert thereference signal in a unit in which the Rx beam direction of the gNBvaries in consideration of variation in the Rx beam direction of thegNB. To this end, a reference signal structure for the concatenated minislots allocated in a RACH resource duration may be desirably defined.The UE to which the data or control channel of a concatenated mini slotformat is allocated in the RACH resource duration should transmit thereference signal of the concatenated mini slot format.

During transmission of a PUSCH or a PUCCH, if one stable gNB Rx beam fora UE Tx beam direction of the PUSCH or the PUCCH is not present or aplurality of beams has similar quality, the PUSCH or a long PUCCH may bestably received by transmitting the PUSCH or the PUCCH throughconcatenated mini slots so as to use a beam diversity characteristic. Inthis case, the gNB may efficiently use a time resource to which a RACHresource is allocated by transmitting the PUSCH or the PUCCH in a RACHresource region.

Additionally, the gNB performs beam tracking for a Tx beam or an Rx beamso that a beam having the best quality is maintained as a serving beamin order to stably maintain a service in a multi-beam environment.Accordingly, the gNB may measure quality of the gNB Rx beam or the UE Txbeam and perform beam tracking by causing the UE to perform repetitivetransmission of the PUSCH, the long PUCCH, or a short PUCCH in each RACHresource region or transmit an RS defined for beam tracking through aplurality of mini slots, using a characteristic in which the gNB changesthe Rx beam in a slot duration to which the RACH resource is allocated.That is, for efficient use of a resource for beam tracking, the gNB maycause the UE to transmit a physical channel suitable for acharacteristic for a time region to which the RACH resource is allocatedand the gNB may use the physical channel as a resource for beamtracking. In other words, for efficient use of the resource for beamtracking, the gNB may indicate, to the UE, that the UE should transmitthe physical channel through a UE Tx beam suitable for each of minislot(s) configured in the time region to which the RACH resource isallocated and the gNB may use the physical channel in each mini slot forbeam tracking. In order for the UE to efficiently transmit a signal forbeam tracking, the gNB informs the UE of information about change in abeam direction as described above and the UE inserts a reference signalinto each Rx beam of the gNB according to this information and apredefined rule and transmits the reference signal. The gNB may use thereference signal as a signal for channel estimation for an Rx beamduration or a signal for signal quality measurement for beam tracking.

Upon transmitting the PUSCH or the long PUCCH which is received in thegNB through beam diversity, since the gNB attempts to receive a signalin each Rx beam duration, antenna gain may have a differentcharacteristic. Therefore, the UE may differently configure transmissionpower of the PUSCH/PUCCH with respect to each Rx beam direction (e.g.,each RACH resource region). To this end, the gNB may inform the UE thatreference channel/signal information and a power control parameter, forpathloss calculation used for open loop power control, should beseparately configured with respect to each RACH resource region. The UEconfigures and transmits different transmission powers in a RACHresource time region using this information.

Unlike this, during transmission of a signal for beam tracking (or beammanagement) in a plurality of RACH resource regions, the respective RACHresource regions should maintain the same transmission power in orderfor a gNB to measure quality of a signal received by the gNB. In thiscase, only one reference channel/signal is needed for control of onepower. If the gNB informs the UE of information about the referencechannel/signal or the information is predefined by a rule, the UE maydetermine the magnitude of transmission power using the referencechannel/signal and transmit the PUSCH/PUCCH by equally applying thetransmission power to all regions.

The gNB may inform the UE of whether UL data or the control channeltransmitted in a RACH resource transmission time region, i.e., a timeregion to which the RACH resource is configured in a corresponding cell,is used for beam diversity or for beam tracking with respect to each ULchannel and cause the UE to perform a power control operation accordingto the above usage.

<PRACH Configuration>

PRACH configuration includes time/frequency information of a RACHresource and may be included in the remaining minimum system information(RMSI). The RMSI may be interpreted as a system information block 1(SIB1) and represents system information that the UE should acquireafter receiving a master system information block (MIB) through aphysical broadcast channel (PBCH). Upon receiving the PRACHconfiguration information, the UE is able to transmit PRACH message 1(Msg1) on a designated time and frequency resource using one preamble ina preamble set included in the PRACH configuration. A preamble format inthe PRACH configuration information may also provide CP length, numberof repetitions, subcarrier spacing, sequence length, etc. Hereinafter,details on the PRACH configuration will be described.

1. RACH Resource Configuration in Time Domain

FIGS. 16 and 17 illustrate RACH resource configuration in the timedomain.

RACH resource configuration in the time domain will now be describedwith reference to FIGS. 16 and 17. Herein, a RACH resource may mean atime/frequency resource in which PRACH Msg1 can be transmitted.Particularly, the RACH resource is associated with an SS block in orderto be able to identify a preferred DL transmission beam direction. EachRACH resource in the time domain is associated with an SS block index.

A set of RACH resources in the time domain may be defined in terms of adefault periodicity of an SS block in a cell. Multiple occasions of RACHresources in the time domain associated with one SS block may be presentwithin the RACH resource set. Referring to FIG. 16, an SS block periodand a RACH resource set period may be configured as illustrated in FIG.16. The RACH resource set period may be determined based on the SS blockperiod and, within the RACH resource set period, multiple RACH resourcesmay be configured. Meanwhile, the RACH resource set period may beconfigured by the PRACH configuration information as described aboveand, in this case, the RACH resource set period may be equal to a PRACHconfiguration period. In the present invention, the PRACH configurationperiod, i.e., a RACH configuration period, may mean a time period inwhich a set of RACH resource(s) occurs according to RACH configuration.

In FIG. 16, each time instance to which a RACH resource is allocated isreferred to as a RACH occasion. That is, when only the time domain andthe frequency domain are considered without considering the sequencedomain, one RACH resource may be referred to as one RACH occasion. Ifthe RACH resource set period is determined based on the SS block period,an exact timing instance may be indicated as an offset from atransmission timing of an SS block associated with a corresponding RACHresource. Exact positions of RACH occasions within the RACH resource setare provided to the UE.

FIG. 17 illustrates a method of indicating association between an SSblock and a RACH resource. Each RACH resource set is configured using anSS block period. An exact starting location in the time domain maydiffer per RACH resource set corresponding to an SS block. Therefore, atiming offset from each SS block to a corresponding RACH resource setmay be signaled.

The duration of a RACH resource is determined by a PRACH preambleformat. The length of a RACH preamble including a guard time (e.g., apreamble format) is configured depending on cell coverage. In addition,the number of preamble repetitions determines the duration of the RACHresource. Therefore, the configuration of the RACH resource includes thenumber of RACH sequence repetitions for indication of a preamble lengthin addition to a RACH preamble format for a CP length.

As described above, in the NR system using multiple beams, an initial DLbeam acquisition procedure is preferentially performed through detectionof the SS block having best reception quality. Thereby, the UE informsthe gNB of information about a preferred DL beam through an initial RACHprocedure. Therefore, in the NR system, the UE may indirectly indicateinformation about a beam index corresponding to an SS block detectedthereby through a resource location for RACH preamble transmission. Forexample, as described with reference to FIG. 5, a RACH resource islinked to each SS block and the UE informs the gNB of the informationabout the beam index in the form of the RACH resource connected to eachSS block. That is, the UE may inform the gNB of a DL beam preferred bythe UE, i.e., an SS block, by transmitting a PRACH using a RACH resourceassociated with the SS block detected by the UE.

Thus, since the time/frequency resource of the RACH resource isbasically connected to the SS block, it is desirable to allocate theRACH resource based on a basic transmission period of the SS block usedin the initial access procedure. However, when there is a small numberof UEs located in a cell of the gNB, the RACH resource may beintermittently allocated compared to the basic transmission period.Therefore, the present invention proposes that a slot to which the RACHresource is allocated be defined as a RACH slot and a periodiocity ofthe RACH slot be configured as a multiple of the basic transmissionperiodiocity of the SS block. Although the above description has beengiven based on a multi-beam environment, it may be efficient even in asingle-beam environment to allocate the RACH resource in the same manneras that in the multi-beam environment, in order to maintain the samestructure as that in the multi-beam environment. In addition, theperiodiocity of the RACH slot may be associated with a RACHconfiguration periodiocity configured by the above-described PRACHconfiguration information. A period of RACH slots in the same locationor having the same index within one RACH configuration period may be thesame as the RACH configuration period. Information about a RACH timeresource among RACH resource allocation information transmitted by anetwork/gNB to the UE may include elements described below.

1) Associated SS block index

2) Location of a RACH slot from an SS block

3) A RACH slot period expressed as a multiple of an SS block period or afunction of the SS block period

4) An offset value for indicating an exact location without ambiguitywhen the RACH slot period relative to the SS block period is greaterthan 1. In this case, the offset value is configured based on subframenumber 0.

In this way, if the time/frequency resource to which the RACH resourceis allocated is associated with the SS block, the number of RACHresources, which corresponds to a timing at which the UE can performRACH transmission, may be basically identical to the number of SSblocks. Generally, although the RACH resource includes all of time,frequency, and code domain resources in which a RACH preamble can betransmitted, the RACH resource in the present invention means atime/frequency resource block in which the RACH preamble can betransmitted, for convenience of description. However, the RACH resourcementioned together with a preamble sequence conceptually includes thesequence domain, i.e., the code domain. For example, if RACH resourcesshare the same time/frequency resource, the RACH resources are one RACHresource in terms of the time/frequency resource but may correspond to aplurality of RACH resources when up to the sequence domain isconsidered.

However, in an environment in which there is a small number of UEswithin the gNB, it may be inefficient to allocate a different RACHresource to each SS block. Therefore, if the gNB may receive RACHpreambles through the same Rx beam or may simultaneously receive theRACH preambles through a plurality of beams, the same time/frequencyresource may be allocated to RACH resources connected to a plurality ofSS blocks. That is, multiple SS blocks may be associated with one RACHtime-frequency resource. In this case, the SS blocks for the RACHresource may be distinguished by preamble indexes or preamble index setsused by the RACH resources. That is, the number of RACH resources may beallocated to be equal to or less than the number of SS blocks.

The gNB determines in which time/frequency region the RACH resourceshould be allocated and informs the UE of related information throughsystem information. In the LTE system, since one or two subframes haveconstituted a RACH slot according to a preamble format, if the gNBdesignates a specific subframe location through the PRACH configurationinformation, the UE could be aware of the location of the RACH resourcein the time domain. On the other hand, in the NR system, informationdifferent from that in the LTE system is required according toconfiguration and environment of the gNB. Particularly, in the NRsystem, a RACH preamble defines a base sequence of a short length due torobustness to a high Doppler frequency, Rx beam scanning, and designmatched for TDD/FDD and configures the base sequence in the form ofrepetition to secure beam scanning and coverage. Hence, there is a highpossibility that the location of the RACH time resource is variableaccording to the gNB or environment. Further, the NR system may beconfigured by a plurality of small cells having a very small size. Inthis case, the length of the RACH preamble becomes very short and a RACHslot in which a plurality of RACH preambles can be transmitted in thetime domain may be configured. For example, RACH time resourceinformation may be provided to the UE as illustrated in FIG. 18.

FIG. 18 illustrates RACH time resource information. Information relatedto a time resource of a RACH resource, i.e., PRACH time resourceinformation, may include the following information:

1) A relative location of a RACH resource/slot to an SS block locationof the RACH resource, or a location of a RACH slot to an SS period;

2) A location of an OFDM symbol on which a RACH resource is startedwithin a RACH slot;

3) A preamble format for a RACH resource (i.e., CP length or sequencelength) and the number of sequence repetitions; and/or

4) Information as to how many RACH resources defined as described aboveare allocated in the time domain. If multiple RACH resources areallocated and the multiple RACH resources are not consecutive in thetime domain, this information indicates information corresponding toeach location, for example, a relative location or an absolute locationof each RACH resource.

Meanwhile, even if RACH resources linked to multiple SS blocks share thesame time/frequency resource, the UE needs to transmit a RACH preambleby discerning to which SS block the RACH resources of the sametime/frequency resource are linked in order to transmit beam acquisitioninformation to the gNB. To this end, available preamble sequences in oneRACH resource need to be separately allocated with respect to each SSblock. In the LTE and NR systems, preamble sequences are configured by acombination of a root sequence for determining a base sequence andcyclic shifted versions of a sequence and orthogonal cover sequenceshaving a zero correlation property within each root sequence. Herein, inorder to raise efficiency of resources, multiple root sequences may beallocated to secure a large number of preamble sequences within the RACHresource. Generally, a cross correlation between the root sequences isgreater than a cross correlation between sequences having differentcyclic shift versions or sequences having different orthogonal covers.In addition, since a signal received from a beam different from a beamsuitable for the UE is weak in reception intensity due to a beamcharacteristic, RACH reception performance is not affected even though across correlation between corresponding sequences has a slightly largevalue with respect to a beam direction different from a beam directionfor the UE. Therefore, if multiple RACH resources share the sametime/frequency resource, it is desirable that the respective RACHresources be configured by preamble sequences having as small a crosscorrelation as possible. As in the above-described embodiment, if RACHpreamble sequences are configured by a combination of a root sequenceand sequences having different cyclic shift versions or differentorthogonal covers within the root sequence, preamble sequences havingdifferent cyclic shift versions within the same root sequence orpreamble sequences having different orthogonal covers within the sameroot sequence may be allocated to RACH resources linked to the samebeam, i.e., one SS block and then different root sequence indexes may beallocated. For example, preamble sequences may be allocated to a RACHtime/frequency resource, as illustrated in FIG. 19.

FIG. 19 illustrates an example of allocating RACH preamble sequences.

Referring to FIG. 19, root sequences {15, 27, 127, 138} are allocated toone time/frequency resource and orthogonal covers {0, 1} and cyclicshift versions {0, 1, 2, 3} are allocated to each root sequence. If twoRACH resources are allocated to the time/frequency resource, a ZC indexconsisting of an OCC index and a cyclic shift version is first allocatedto a RACH resource linked to an N-th SS block and a RACH preamblesequence set consisting of two root sequences {15, 27} is allocated. TheRACH preamble sequence set is also allocated in the same order to a RACHresource linked to an (N+1)-th SS block. To inform the UE of the RACHresource, the gNB informs the UE of information for configuring a RACHpreamble sequence set for each RACH resource and determines an order ofRACH preamble sequences within a RACH preamble sequence set by apredefined rule. According to the predefined rule, a RACH preamblesequence index first increases with respect to {OCC index, cyclic shiftversion} and the next RACH preamble sequence index increases based on aroot sequence index. That is, the RACH preamble sequence indexpreferentially increases according to an order of a low crosscorrelation between sequences.

2. RACH Resource Configuration in Frequency Domain

PRACH configuration may provide a RACH resource in the frequency domain.When the UE attempts to transmit a PRACH in a situation in which the UEhas not yet connected to a cell, the UE may not be aware of whole systembandwidth or resource block indexing.

In the LTE system, an SS is transmitted in the center of systembandwidth and a PBCH provides the system bandwidth so that the UE mayeasily obtain an exact location of a RACH resource. However, in the NRsystem, the SS is not guaranteed to be transmitted in the center of thesystem bandwidth. Therefore, in the NR system, it may not be easy toobtain resource block indexing when the UE transmits the PRACH. Hence, amethod of providing a RACH resource location in the frequency domain isneeded.

UEs in an idle mode acquire frequency synchronization based on an SSblock and therefore it is preferable that information about a frequencylocation of a RACH resource is provided in terms of SS block bandwidth.The RACH resource in the frequency domain should be located within abandwidth of the SS block in which the UE detects the SS block. Thetransmission bandwidth of a RACH preamble has a fixed value with a 15kHz default subcarrier spacing of a PSS/SSS/PBCH. For example, thetransmission bandwidth of the RACH preamble may be fixed to 1.08 MHz ata 15 kHz default subcarrier spacing. If the transmission bandwidth ofthe RACH preamble is 1.08 MHz, the transmission bandwidth of the SSblock assumed to have a 15 kHz subcarrier spacing is four times thetransmission bandwidth of the RACH preamble. A network needs to providean exact location of the RACH resource in the frequency domain withinthe SS block.

If the network configures a RACH resource outside an SS block in whichthe PSS/SSS/PBCH is transmitted, information about the RACH resourceshould be signaled based on a bandwidth of the SS block and a bandwidthof the RACH resource. Whole system bandwidth is indexed in units of SSblock bandwidth.

3. Number of Resources in Time Domain

If a short ZC sequence is used for an NR PRACH preamble, the short ZCsequence may cause sequence shortage in a time resource (defined as a CPand a RACH preamble). In order to overcome this problem, multiple timeand frequency resources in a RACH may be allocated for a RACH resourceand the gNB needs to inform the UE of how many time resources are usedin a RACH slot in addition to frequency resource information.

4. Sequence Information

In the LTE system, 64 sequences are allocated to a RACH resource. If aroot code (i.e., root sequence) is assigned, then a cyclic shift versionof the root code is first mapped to a preamble index before use ofanother root code due to a zero cross correlation property.

An NR PRACH may reuse the same property. Sequences with the zero crosscorrelation property may be first allocated for a RACH preamble. Thezero cross correlation is provided by a cyclic shift version and apredefined orthogonal cover (if defined). If a root code is assigned,then the orthogonal cover is allocated by a predefined rule orconfiguration and the cyclic shift version with the root code and theorthogonal cover is mapped to a preamble index.

In summary, PRACH configuration signaled to the UE by the gNB mayinclude the following parameters:

-   -   RACH resource allocation in the time/frequency domain: Preamble        format (a CP duration and the number of repetitions of a ZC        sequence)    -   Sequence information: Root code index, orthogonal cover index        (if defined), cyclic shift length

5. Association Between RACH Resource and SS Block Index

Hereinafter, a method of signaling link information between transmissionbeam directions of the gNB and RACH resources in an initial access stateto the UE will be described in detail. The transmission beam directionof the gNB refers to a beam direction of an SS block as described aboveand, when the UE can observe/measure a specific RS in addition to the SSblock in the initial access state, the transmission beam direction ofthe gNB may additionally refer to the corresponding RS. For example, thespecific RS may be a CSI-RS.

In NR, a plurality of SS blocks may be formed and transmitted accordingto the number of beams of the gNB. Each SS block may have a uniqueindex. The UE may derive an index of an SS block to which acorresponding PSS/SSS/PBCH belongs by detecting the PSS/SSS and decodinga PBCH. Next, system information transmitted by the gNB includes RACHconfiguration information. The RACH configuration information mayinclude a list of multiple RACH resources, information for identifyingthe multiple RACH resources, and link information between each RACHresource and each SS block.

In the above description, the RACH resource has been limited to atime/frequency resource in which the UE is capable of transmitting thePRACH preamble. Likewise, in a description given below, the RACHresource is also limited to the time/frequency resource. Hereinafter, amethod for indicating a RACH location in the frequency domain as well asa RACH location in the time domain will be described. As describedabove, one RACH resource has been linked to one or more SS blocks andconsecutive RACH resources in the time domain have been defined as theRACH resource set. Plural RACH resource sets which are consecutive inthe frequency domain as well as in the time domain are defined as oneRACH resource block.

FIG. 20 illustrates a RACH resource block.

As illustrated in FIG. 20, the RACH resource block may be defined as onetime/frequency chunk in which RACH resources are gathered. RespectiveRACH resources in the RACH resource block have unique indexes determinedby time/frequency locations.

RACH resource indexes in the RACH resource block are mapped by aspecific rule. For example, the RACH resource indexes may be assigned ina frequency-time order or time-frequency order. For example, referringto FIG. 20, in the case of the frequency-time order, RACH resources inthe RACH resource block may be indexed as follows.

-   -   RACH resource #0 (time, frequency): (0,0),    -   RACH resource #1: (1, 0)    -   RACH resource #2: (2, 0)    -   . . . . .

Herein, a unit of a time axis length in the RACH resource block may bedetermined by a RACH preamble format and a unit of a frequency axislength may be determined by a unit of a RACH resource bandwidth (e.g.,1.08 MHz) or a resource block group (RBG).

Meanwhile, when the UE requests system information transmission bytransmitting a specific RACH preamble, a plurality of RACH resourceblocks may be designated in one system/cell according to the number ofSS blocks or for the purpose of transmitting system information.Especially, when there are a large number of SS blocks, if all RACHresources corresponding to the respective SS blocks are consecutivelyconfigured as mentioned above, severe restrictions may be imposed on aUL/DL data service. Therefore, the network may configure consecutiveRACH resources in the time/frequency domain as a RACH resource block anddiscontinuously arrange each of the configured RACH resource blocks.Thus, a plurality of RACH resource blocks may be configured and each ofthe RACH resource blocks may also have a unique index.

In other words, a duration in which RACH resource block(s) areconfigured (hereinafter, a RACH configuration duration) may bedesignated in one system/cell and one or more RACH blocks may be presentin the RACH configuration duration. FIG. 21 illustrates a RACHconfiguration duration according to the present invention. Informationof which the network/gNB should inform the UE may include the length ofthe RACH configuration duration, the number of RACH resource blocks(i.e., RACH blocks), and the location of each RACH block. As illustratedin FIG. 21, intervals between RACH blocks within the RACH configurationduration may be indicated to the UE. For example, the network/gNB mayinform the UE of a relative location from RACH block #0, such as thenumber of slots or offset information of an absolute time unit, as RACHblock location information, or may directly inform the UE of a startslot index of each RACH block within the RACH configuration duration.

Each RACH resource within each RACH resource block may have a uniqueconfiguration. In this case, occurrence frequency and period of eachRACH resource may differ with respect to and each RACH resource may belinked to a specific SS block, CSI-RS, or DL beam direction. In thislink relationship, information about this link relation is provided tothe UE. FIG. 22 illustrates a configuration of each RACH resource withina RACH resource block. Slot indexes that can be reserved as RACHresources in a specific RACH resource period may be defined in thestandard document. As illustrated in FIG. 22, different configurationnumbers may be allocated according to an occurrence frequency of a RACHresource. The network/gNB may inform the UE of an occurrencefrequency/period of a specific RACH resource by indicating a specificconfiguration number through system information.

The network may inform the UE of the number of RACH resource blocks(i.e., RACH blocks) and a starting time (e.g., slot index) of each RACHresource block. In addition, upon informing the UE of information abouteach RACH resource block, the network informs the UE of the number Nt ofRACH resources in the time domain and the number Nf of RACH resources inthe frequency domain. Nt and Nf may differ according to each RACHresource block. The network/gNB maps RACH resource indexes in the RACHresource block according to the time/frequency locations of RACHresources and informs the UE of information indicating aperiod/occurrence frequency of each RACH resource (e.g., configurationnumber) and information about a linked SS block or CSI-RS index. In thiscase, the period/occurrence frequency of each RACH resource may beindicated to the UE by indicating a specific configuration number whichis configured according to the occurrence frequency of the RACH resourceas described above.

In addition, a RACH preamble format may be configured with respect toeach RACH resource. Although all RACH preamble formats may be equallyconfigured in a system, the above-described RACH preamble formats may bedifferently configured between RACH resource blocks while equallymaintaining a subcarrier spacing and the number of repetitions withinthe RACH resource block in reality. Notably, although the number ofrepetitions of the RACH preamble within the same RACH resource block maybe equally configured, respective RACH resources included in the RACHresource block may be configured to use different preamble sequences.For example, respective RACH resources in the RACH resource block may beconfigured to use different root indexes or cyclic shift (CS) versions.

In summary, in terms of signaling for a RACH configuration, the networkperforms a procedure of identifying a time/frequency resource for RACHpreamble transmission, i.e., a RACH resource. To this end, in thepresent invention, a RACH resource index is determined by a RACHresource block index and by a RACH resource index within the RACHresource block and the occurrence frequency/period of the RACH resourceof each RACH resource index may correspond to each of plural RACHconfiguration numbers. Additionally, the network transmits, to the UE,information about a RACH preamble capable of being used in each RACHresource and information about a linked SS block index or CSI-RS index.Thereby, the UE may acquire information about a RACH time/frequencyresource and preamble resource to be used when performing a RACHprocedure for a specific DL beam direction and perform the RACHprocedure using the corresponding resource.

<RACH Preamble Formats for Slot/Symbol Boundary Alignment>

Hereinafter, the RACH preamble format described with reference to FIG.10 will be described in detail. In consideration of features andrequirements of the RACH preamble format in NR described in FIG. 10, therelationship between the RACH resource and the RACH preamble formataccording to the present invention is described and how RACH preambleformats of the present invention are aligned with a UL slot and a slotboundary of the NR system is explained.

Generally, a sequence part of the RACH preamble in LTE uses a length-839ZC sequence having a subcarrier spacing (SCS) of 1.25 kHz and the RACHpreamble in LTE usually occupies a subframe of 1 ms. RACH preambleformats in the LTE system are listed in Table 1. Although RACH preambleshave the same sequence length, if coverage ranges that the RACHpreambles desire to support are different, the RACH preambles may havedifferent CP lengths. As a CP length increases, coverage that can besupported by a corresponding cell increases and, as a CP lengthdecreases, coverage that can be supported by a corresponding celldecreases. As the length of a sequence constituting a preambleincreases, since a receiver may receive a signal by gathering muchenergy, combining gain can be obtained and therefore detectionperformance of a RACH can be improved.

In the NR system, two types of RACH sequence may be defined. Similarlyto the case of the LTE system, a long sequence for the purpose ofsupporting wide coverage and a short sequence for RACH repetition of theUE and Rx beam sweeping of the gNB may be defined. The short sequencehas not only a purpose of RACH repetition by the UE and Rx beam sweepingby the gNB but also a purpose of supporting high speed and immediatelyproviding a service which is critical to latency of a communicationsystem by not reserving an excessively long UL resource.

The long RACH sequence for supporting wide coverage may be introduced tothe NR system in a similar form to that of the LTE system by using aRACH sequence of the LTE system or modifying a part of the RACH sequenceof the LTE system. However, in the short RACH sequence, a preambleformat should be designed to be suitable for the purpose of the shortRACH sequence and a RACH resource in which a corresponding RACH preambleis transmitted should be able to well match UL PUSCH transmission.

FIG. 23 illustrates a slot structure. Particularly, FIG. 23(a)illustrates a slot structure in a slot having 14 symbols and FIG. 23(b)illustrates a slot structure in a slot having 7 symbols. In NR, it isconsidered configuring one slot as 7 symbols or 14 symbols. In FIG. 23,“DD/UD” means that DL data or UL data can be scheduled on acorresponding symbol. Likewise, in FIG. 23, “Gap/DC/DD” means that agap, DL control, or DL data can be transmitted after a DL control (DC)symbol, which is the first symbol.

The present invention proposes a method for the network to efficientlyuse a RACH resource and a UL data (e.g., PUSCH) resource. In the presentinvention, an SCS of a short RACH sequence uses the same value as adefault PUSCH SCS of a corresponding cell so as to match sampling ratesof a PRACH and a PUSCH.

FIG. 24 illustrates a RACH preamble format in an OFDM symbol. Asillustrated in FIG. 24, if one symbol RACH preamble is transmitted usinga short RACH sequence, a CP length becomes too short so that coveragethat can be supported by the corresponding RACH preamble becomes toonarrow. Therefore, one symbol RACH preamble may not function as anactual RACH preamble. Accordingly, in the present invention, two symbolsare configured as the smallest RACH symbol unit during transmission of ashort RACH sequence and, if necessary, the CP length may increase or thenumber of repetitions may be adjusted by extending the number of RACHsymbols. The number of RACH symbols may be extended to a multiple of abasic unit.

FIGS. 25 and 26 illustrate alignment of RACH preambles in a slot.Particularly, FIGS. 25 and 26 illustrate symbol locations at which PRACHpreambles can be transmitted in a slot having 14 symbols when a RACHpreamble has a length of 2, 4, 6, or 12 symbols, i.e., RACH resources ina slot. In FIGS. 25 and 26, “RACH(x)” indicates the number ofrepetitions of a preamble (i.e., the number of repetitions of a RACHsequence). Hereinafter, “RACH(x)” is referred to as x symbol RACHs, xsymbol RACH resources, or x symbol RACH preambles.

Referring to FIG. 25(a), in the case of a 14-symbol RACH, i.e., a RACHin which a RACH preamble of a 1-symbol length is repeated 14 times, theRACH preamble occupies all of a slot of a 1-ms length. If a signal otherthan the RACH preamble is transmitted, i.e., if DL control/data or ULcontrol/data is transmitted, in an adjacent slot immediately after theslot in which the RACH preamble is transmitted, the adjacentdata/control signal should be protected by inserting a guard time (GT)into the last end of the RACH preamble repeated 14 times so as not totransmit a signal during a predetermined time. Similarly, in the case ofa RACH in which one preamble is repeated 12 times, for example, in thecase of a 12-symbol RACH of FIG. 25(b), if a data/control signal otherthan the RACH preamble is transmitted on a symbol immediately after theRACH, the GT is inserted into the rear part of the RACH preamble. FIG.25(a) illustrates a preamble format capable of being used when acorresponding slot is a UL only slot. As DL control, if the first OFDMsymbol of the corresponding slot is used and the last 14th symbol isreserved for UL control transmission, a RACH preamble format having thelongest length is illustrated in FIG. 25(b).

Assuming that one symbol for DL control and one symbol for UL controlare used, locations at which RACH preambles can be transmitted in oneslot with respect to a 2-symbol RACH, a 4-symbol RACH, and a 6-symbolRACH are illustrated in FIGS. 25 and 26. In FIG. 25, a RACH resource isconfigured at locations except for the first and last symbols so thatthe first symbol of a slot may be used for DL control and a UL controlregion of the last symbol may be protected, except for FIG. 25(a)illustrating a RACH preamble format of a 14-symbol length. In FIG. 26, aDL control signal of the first symbol is avoided, the second symbol isemptied in consideration of a DL-to-UL switching time of the gNB, and aRACH preamble is transmitted starting from the third symbol. If the RACHpreamble is configured to occupy symbols up to a UL control region whichis the last symbol of a slot, a RACH signal is prioritized over ULcontrol in a corresponding symbol duration. That is, if a specifictime/frequency resource in a time/frequency region in which the UEshould transmit UL control is configured as a RACH resource, the UEdrops UL control transmission in the corresponding time/frequencyresource.

As illustrated in FIGS. 25 and 26(b) to 26(e), a plurality of RACHresources may be configured in one slot configured for a RACH and theRACH resources may be consecutive. When the network configures themultiple RACH resources, if the multiple RACH resources are concatenatedin the time domain, a GT does not have to be inserted between theconcatenated RACH resources on the premise that a CP length of RACHpreambles transmitted in the concatenated RACH resources is sufficient.That is, if a set of the concatenated RACH resources in the time domainis referred to as a RACH block (or RACH burst), the GT does not have tobe inserted into a RACH preamble transmitted in a RACH resource within aRACH block. Herein, the meaning of “the GT is inserted” is that a signalis not transmitted during a corresponding time duration, i.e., acorresponding time duration is null. The GT is inserted into a RACHpreamble transmitted in the rearmost RACH resource in the time domainwithin a RACH block, i.e., a gap time at which signal transmission isnot performed during a predetermined time duration is configured, sothat other signals transmitted after the RACH preamble are protected. Inthe case of a RACH preamble format including repetition of a preamble,consecutive signals are transmitted in a RACH resource even if thepreamble is repeated.

When the RACH preamble is repeatedly transmitted, if the number ofrepetitions increases, i.e., if the number of symbols used for RACHtransmission increases, a CP length may increase. In the case of twosymbols for example, although a data transmission format in the twosymbols is configured in the form of CP−data-CP−data, i.e., althoughCP+data are transmitted on one of the two symbols and CP+data aretransmitted on the other one of the two symbols, the RACH preamble maybe transmitted in the form of CP-CP-sequence-sequence-(GT) for coverageexpansion. FIG. 27 illustrates RACH preamble formats for aligning a RACHpreamble and a symbol boundary by increasing a CP length according tothe present invention. Specifically, FIG. 27 illustrates increasing a CPlength according to the number of repetitions of a RACH preamble. Then,cell coverage supported by a corresponding RACH preamble format can beextended by repeating the RACH preamble, i.e., repeating a RACHsequence. In the RACH preamble format of FIG. 27, the GT is locatedwithin the last RACH resource of the RACH block in the time domain.

FIG. 28 illustrates a RACH resource in a slot consisting of 7 symbolsand RACH preamble mapping according to the number of preamblerepetitions. As described above, when other data/control signals aretransmitted after a RACH resource, the GT is inserted into a RACHresource immediately before the data/control signals. That is, duringthe GT, signals are not transmitted and are emptied.

FIG. 29 a null OFDM symbol located after a RACH symbol.

The GT is inserted into a point at which concatenated RACH resources areended, i.e., at the last location of a RACH block, thereby protecting asubsequent signal. Another method of protecting the subsequent signal isto empty a symbol after the RACH resources, i.e., a symbol immediatelyafter the RACH block. In other words, no signals are transmitted on asymbol immediately after the RACH block. If the symbol after the RACHblock is null, the GT does not have to be inserted into the last symbolof the RACH block. A corresponding null OFDM symbol is used as the GT byemptying the symbol immediately after the RACH block and a signaltransmitted after the null OFDM symbol can be protected. For making aspecific OFDM symbol null, the specific OFDM symbol may be pre-signaledby the gNB to the UE or designated by the standards. For example, whiletransmitting PRACH configuration to the UE, the gNB may signal, to theUE, that a specific symbol is null. Alternatively, when the gNBconfigures concatenated RACH resources in the time domain, the UE mayreceive all of this information and it may be promised between the UEand the gNB that a time point at which consecutive RACH resources areended, i.e., a symbol immediately after a RACH block, is null.Alternatively, whether the symbol immediately after the RACH block isnull may be signaled. If the gNB commands that the symbol immediatelyafter the RACH block be null, the UE may make the symbol immediatelyafter the RACH block null and does not include the GT in a RACH preamblewithin the RACH block. Upon receiving a command indicating that thesymbol immediately after the RACH block should not be null, if the UEtransmits a preamble in the rearmost RACH resource within the RACH blockin the time domain, the UE configures the GT during which a signal isnot transmitted after transmitting the preamble, in a corresponding RACHresource.

An advantage of the method in which RACH resources are concatenated inthe time domain is that there is no need to insert the GT into everyRACH preamble. Since a CP length of a RACH preamble transmitted in aRACH resource transmitted immediately after one RACH preamble issufficiently long, a corresponding CP may be used as the GP of a RACHpreamble transmitted in a previous RACH resource. Therefore, the presentinvention proposes first indexing RACH resources in the time domain andnext indexing the RACH resources in the frequency domain. That is,referring to FIG. 20, RACH resources are first configured in the timedomain. Next, if the RACH resources are not enough than what is needed,the RACH resources may be further configured in the frequency domain.Accordingly, indexing of RACH resources within a RACH block aredesirably performed first in the time domain.

Hereinafter, a method of multiplexing RACH resources for RACH preambleformats having different repetition lengths in the same slot will bedescribed with reference to FIG. 30. FIG. 30 illustrates a method ofmultiplexing RACH resources in a slot. In FIG. 30, “RACH(x)” indicatesthe number of repetitions of a preamble (i.e., the number of repetitionsof a RACH sequence) in a corresponding RACH resource. Hereinafter,“RACH(x)” is referred to as x symbol RACHs, x symbol RACH resources, orx symbol RACH preambles.

In consideration of multiple beams, target DL Rx directions between RACHresources located in different frequencies at the same time should bethe same. That is, Rx directions of the gNB should be the same. Forexample, referring to FIG. 30(a), an Rx direction of the gNB for a6-symbol RACH resource (“RACH(6)” in FIG. 30) starting on a symbol ofindex 3 should be equal to an Rx direction of the gNB of RACH(4) andRACH(2), nested by the corresponding RACH resource at a correspondingtime, i.e., located within a symbol boundary of RACH(6). This means thatDL channels/signals of the gNB associated with RACH resources should beequal and, typically, this may mean that indexes of SS blocks associatedwith corresponding RACH resources should be equal. For example,referring to FIG. 30(a), RACH(6) may be used for a RACH preamble formathaving a RACH sequence repeated 6 times. RACH(4) and RACH(2) infrequencies different from frequencies of RACH(6) within a time durationof RACH(6), may be formed such that one RACH(4) for a RACH preambleformat having a RACH sequence repeated 4 times and one RACH(2) for aRACH preamble format having a RACH sequence repeated twice areconsecutively configured in the time domain. Alternatively, 3 RACH(2)may be consecutively configured in the time domain in frequenciesdifferent from frequencies of RACH(6) within the time duration ofRACH(6). Thus, this method of configuring different RACH resources byvarying lengths of RACH sequences, consequently, by varying the RACHpreamble formats, even when the RACH sequences are associated with thesame SS block may be used to distinguish between a contention-based RACHresource and a contention-free RACH resource or to configure anadditional RACH resource for requesting system information when RACHtransmission is used for a system information request. Generally, a RACHresource for contention-based initial access may occupy a long length(i.e., a large number) of symbols and a RACH resource having a purposeof handover having a high possibility that the UE discerns coverage of atarget cell to some degree or a system information request may occupy arelatively short length (i.e., small number) of symbols.

Hereinafter, a RACH preamble format in the NR system will be proposed indetail based on the above description of the present invention.Regarding the RACH preamble format for the NR system, the presentinvention has assumed that a data symbol length (i.e., an effectivesymbol duration corresponding to a pure data/information signal) in oneOFDM symbol is 2048*T_(s) and a CP length in one OFDM symbol is144*T_(s). Therefore, the length of one OFDM symbol available for datatransmission is (2048+144)*T_(s), where T_(s) is a sampling time.Hereinafter, for convenience of description, T_(s) will be omitted inmentioning a symbol length. Table 8 lists numerologies based on thelength of one OFDM symbol of a preamble having an SCS of 15 kHz and aRACH sequence length of 139. In Table 8, an effective symbol length of2048 is a length other than a CP in an OFDM symbol duration.Particularly, Table 8 shows numerologies of an OFDM symbol constitutinga slot when a sampling frequency is 30.72 MHz and a time sampling unitis T_(s)=1/(15000*2048) based on an SCS of 15 kHz and FFT of 2048. Inthis case, a multipath profile supported by a length-144 CP is a maximumof 4.68 μsec.

TABLE 8 Effective symbol length (T_(s)) 2048 CP length (T_(s)) 144Sequence length 139 Subcarrier spacing (kHz) 15 Multipath profile (μsec)4.69 Sampling frequency (MHz) 30.72

In numerologies for SCSs of 30 kHz, 60 kHz, and 120 kHz, T_(s) is scaledto be inversely proportional to T_(s) for 15 kHz depending on how manytimes 15 kHz the SCS is. However, the effective symbol length and the CPlength of an OFDM symbol are basically maintained at 2048 and 144,respectively.

The following tables show preamble formats according to the presentinvention. Particularly, Table 9 shows preamble formats in the case of apreamble sequence with an SCS of 15 kHz, Table 10 shows preamble formatsin the case of a preamble sequence with an SCS of 30 kHz, Table 11 showspreamble formats in the case of a preamble sequence with an SCS of 60kHz, and Table 12 shows preamble formats in the case of a preamblesequence with an SCS of 120 kHz. In Tables 9 to 11, a guard period isconfigured on an OFDM symbol after the end of a RACH burst for preambleformat A1 or A2.

TABLE 9 Number of Effective Cell Preamble Symbol CP sequence symbolGuard radius format duration length repetitions length period (meter) 1A1 2 288 2 4096 2048 703 A2 2 2336 1 2048 2048 9297 B 2 1240 1 2048 10965352 2 A1 4 576 4 8192 2048 2109 A2 4 2624 3 6144 2048 9297 B 4 1384 36144 1240 6055 3 A1 6 864 6 12288 2048 3516 A2 6 2912 5 10240 2048 9297B 6 1528 5 10240 1384 6758 4 A1 12 1728 12 24576 2048 7734 A2 12 3776 1122528 2048 9297 B 12 1960 11 22528 1816 8867 5 A1 14 2016 14 28672 20489141 A2 14 4064 13 26624 2048 9297 B 14 2104 13 26624 1960 9297

TABLE 10 Number of Effective Cell Preamble Symbol CP sequence symbolGuard radius format duration length repetitions length period (meter) 1A1 2 288 2 4096 2048 352 A2 2 2336 1 2048 2048 4648 B 2 1240 1 2048 10962676 2 A1 4 576 4 8192 2048 1055 A2 4 2624 3 6144 2048 4648 B 4 1384 36144 1240 3027 3 A1 6 864 6 12288 2048 1758 A2 6 2912 5 10240 2048 4648B 6 1528 5 10240 1384 3379 4 A1 12 1728 12 24576 2048 3867 A2 12 3776 1122528 2048 4648 B 12 1960 11 22528 1816 4434 5 A1 14 2016 14 28672 20484570 A2 14 4064 13 26624 2048 4648 B 14 2104 13 26624 1960 4648

TABLE 11 Number of Effective Cell Preamble Symbol CP sequence symbolGuard radius format duration length repetitions length period (meter) 1A1 2 288 2 4096 2048 176 A2 2 2336 1 2048 2048 2324 B 2 1240 1 2048 10961338 2 A1 4 576 4 8192 2048 527 A2 4 2624 3 6144 2048 2324 B 4 1384 36144 1240 1514 3 A1 6 864 6 12288 2048 879 A2 6 2912 5 10240 2048 2324 B6 1528 5 10240 1384 1689 4 A1 12 1728 12 24576 2048 1934 A2 12 3776 1122528 2048 2324 B 12 1960 11 22528 1816 2217 5 A1 14 2016 14 28672 20482285 A2 14 4064 13 26624 2048 2324 B 14 2104 13 26624 1960 2324

TABLE 12 Number of Effective Cell Preamble Symbol CP sequence symbolGuard radius format duration length repetitions length period (meter) 1A1 2 288 2 4096 2048 88 A2 2 2336 1 2048 2048 1162 B 2 1240 1 2048 1096669 2 A1 4 576 4 8192 2048 264 A2 4 2624 3 6144 2048 1162 B 4 1384 36144 1240 757 3 A1 6 864 6 12288 2048 439 A2 6 2912 5 10240 2048 1162 B6 1528 5 10240 1384 845 4 A1 12 1728 12 24576 2048 967 A2 12 3776 1122528 2048 1162 B 12 1960 11 22528 1816 1108 5 A1 14 2016 14 28672 20481143 A2 14 4064 13 26624 2048 1162 B 14 2104 13 26624 1960 1162

In Table 9 to Table 12, an effective symbol length is a length of a partother than a CP in a RACH preamble, i.e., a length T_(SEQ) of a sequencepart.

Preamble formats for the NR system proposed in the present inventionwill be described in detail based on preamble format 1 of Table 9.Preamble format 1 corresponds to the case in which a RACH preamble has alength of two symbols and the same preamble is repeated twice on the twosymbols. FIG. 31 illustrates a transmission format of a RACH preamble ofa 2-symbol length (hereinafter, a 2-symbol RACH preamble) aligned withtwo symbols. If a RACH resource of a 2-symbol length is configured forthe UE that transmits a RACH preamble and a RACH preamble formatsuitable for the RACH resource is indicated, the UE transmits a preambleof a 2048-sample length by repeating twice after a CP of a 288-samplelength as illustrated in FIG. 31. However, when the gNB receives theRACH preamble as illustrated in FIG. 31, cell coverage capable of beingsupported by the RACH preamble differs according to which scheme the gNBuses upon receiving the RACH preamble.

FIG. 32 illustrates preamble formats corresponding to preamble format 1of Table 9. Particularly, FIG. 32(a) illustrates A2 of preamble format 1(hereinafter, preamble format 1-A2) of Table 9, FIG. 32(b) illustratesA1 of preamble format 1 (hereinafter, preamble format 1-A1) of Table 9,and FIG. 32(c) illustrates B of preamble format 1 (hereinafter, preambleformat 1-B) of Table 9.

Referring to FIG. 32(a), for example, in preamble format 1-A2 of Table9, the gNB receives a RACH preamble under the assumption that the RACHpreamble is a signal repeated once. In this case, the gNB assumes that apart other than a 2048-length sequence consists of a CP and a guardperiod (GP) (which is the same as GT). Notably, the gNB receives theRACH preamble under the assumption that a maximum of 2048 samples aftera sequence of the RACH preamble is the GP according to preamble format1-A2. When RACH resources are concatenated, since a CP length of theconcatenated RACH resources is sufficient, there is no problem inreceiving another RACH preamble in an adjacent RACH resource even if thegNB receives the RACH preamble under the assumption that a CP durationof a subsequent RACH preamble is the GP. Therefore, in preamble format1-A2 of Table 9, in terms of reception by the gNB, a CP length may beregarded as 2336, a GP length may be regarded as 2048, and the number ofrepetitions of the RACH preamble is 1. Due to a sufficient GP length,the corresponding format may support a maximum cell radius up to 9297 m.

Unlike this, in a cell having a small cell radius, the gNB may receive aRACH preamble that the UE has transmitted in the form illustrated inFIG. 31 by regarding the RACH preamble is a preamble sequence signalrepeated twice. That is, referring to FIG. 32(b), it may be assumed thata CP length is 288 and a sequence part length is 4096. The sequence partof the RACH preamble may be understood as a signal obtained by repeatinga length-2048 sequence twice. This corresponds to preamble format 1-A1.Obviously, the GP may be secured by making a symbol after acorresponding RACH resource, i.e., a symbol subsequent to the RACHresource, null. Alternatively, if the GP is within a CP length of thesubsequent symbol, an actual GP length is limited by the length of asubsequent CP. That is, in the case of the GP of a RACH preamble, asymbol after the RACH preamble may be null and a CP of a signaltransmitted on the subsequent symbol may be used as the GP. In thelatter case, however, since the CP of the subsequent signal is used asthe GP, the GP length cannot be greater than the CP length. In otherwords, when RACH resources are consecutive in the time domain, if asignal subsequent to one arbitrary RACH resource other than the lastRACH resource among consecutive RACH resources is a RACH preamble andthe RACH preamble adjacent to the RACH resource is preamble format 1-A1,a CP length of the RACH preamble becomes 288. Consequently, in preambleformat 1-A1, a maximum radius capable of being supported by thecorresponding preamble format is limited by the CP length and the GPlength. As shown in Table 9, if the RACH preamble is 15 kHz, a maximumcell radius supported by preamble format 1-A1 format is 703 m.

Unlike this, in preamble format 1-B, all of a CP, a sequence, and a GPmay be designed to be included in one RACH resource. That is, althoughthe UE transmits a sequence through repetition two times as illustratedin FIG. 31, the gNB detects the sequence by securing both a CP and a GPwithin a corresponding RACH preamble transmission duration. In thiscase, referring to FIG. 32(c), if one RACH preamble occupies twosymbols, the gNB may regard a maximum number of repetitions of thesequence as one. If one RACH preamble occupies N symbols, the gNB mayregard the number of sequence repetitions as N−1.

To generalize the present invention, the case in which 6 symbols areused to transmit the RACH preamble will now be described, by way ofexample, with reference to Table 9 in which an SCS of the RACH preambleis 15 kHz. If a RACH preamble format using 6 symbols for RACH preambletransmission is referred to as preamble format 3, in preamble format3-B, the UE transmits a CP of a length corresponding to 6 times a dataCP length during a corresponding RACH resource duration, i.e., during a6-OFDM symbol duration, and transmits the same preamble throughrepetition 6 times, as described with respect to preamble format 1-B.However, upon receiving the preamble, the gNB assumes that the preamblehas been repeated five times in order to secure a GP within thecorresponding RACH resource and the gNB obtains 5 other than 6 asrepetition gain for the corresponding RACH preamble. Since the UEtransmits the same preamble through repetition 6 times, when the gNBdesires to obtain repetition gain of 6 times (preamble format 3-A1), amaximum cell radius supported by the corresponding preamble sequence is3516 m and, when the gNB desires to obtain repetition gain of five times(preamble format 3-A2), a maximum cell radius supported by thecorresponding preamble sequence is 9297 m. In other words, when the gNBcommands the UE to transmit the RACH preamble with a preamble formathaving a preamble repeated 6 times, if a cell radius of the gNB is lessthan 3516 m, the gNB may obtain repetition gain of 6 times from the RACHpreamble. However, if the gNB supports a greater cell radius than 3516m, repetition gain that can be obtained by the gNB is only 5 times.

In other words, in Table 9 to Table 12, numbers in preamble formats 1,2, 3, 4, and 5 are values indicating how many times the RACH preambleare repeatedly transmitted during a duration of corresponding symbols bythe UE. Preamble format 1 means repetition two times (or 2 symbols),preamble format 2 means repetitions four times (or 4 symbols), preambleformat 3 means repetition 6 times (or 6 symbols), preamble format 4means repetition 12 times (or 12 symbols), and preamble format 5 meansrepetition 14 times (or 14 symbols). In Table 9 to Table 12, A1, A2, andB indicate a scheme in which the gNB detects a corresponding signalaccording to a cell radius. In which manner the gNB is to detect a RACHpreamble may be an implementation issue but a cyclic shift value (i.e.,N_(CS)) of a RACH sequence that the UE can use or the gNB can detect maydiffer depending to how the gNB performs detection. That is, when a cellradius is large, if adjacent CSs are used with respect to ZC sequenceshaving the same root index, this may deteriorate RACH performance.Therefore, in this case, it is desirable to use/allocate CSs having abig difference.

In Table 9 to Table 12, preamble formats 4 and 5 are formats in which apreamble is repeated 12 times and 14 times, respectively. As opposed topreamble formats 1, 2, and 3, it may be understood that format A1 or A2hardly obtains gain relative to format B. In preamble formats 1, 2, and3, gain of format A1 or A2 relative to format B is support of a widecell radius, whereas, in preamble formats 4 and 5, it is difficult toconsider that plural RACH resources having a corresponding length in aslot are consecutively present. Particularly, in the case of preambleformat 5, since all of 14 symbols are used as a RACH resource, onesymbol after 14 symbols should be null for cell radius expansion.However, since it is burdensome to make a symbol on which a DL controlchannel of a subsequent slot should be transmitted null, preamble format5 inevitably uses only a GP capable of being occupied in a RACHresource. Therefore, in preamble format 5, a maximum cell radius isdetermined by a GP that can be secured within 14 symbols rather than anadditionally securable GP. Similarly to preamble format 5, in preambleformat 4, the maximum cell radius is determined by a GP that can besecured in the RACH resource. Accordingly, preamble formats 4 and 5desirably support only format B rather than format A1 and/or A2.

On the other hand, in preamble formats 1, 2, and 3, format A2 and formatB may obtain the same repetition gain, whereas a cell radius supportedby format B is smaller than a cell radius supported by format A2.Therefore, it is desirable for preamble formats 1, 2, and 3 to supportonly format A1 and/or A2 and not to support format B.

In the NR standard document, distinguishment between formats A1 and A2and format B may be meaningless. However, when a RACH preamble format isspecified, since a cell radius supported by the RACH preamble formatshould be definite, the corresponding formats may be separately definedfor the above purpose. Particularly, in formats A1 and A2, a CS of aPRACH preamble becomes different due to a difference between cellradiuses that can be supported by the respective formats and therefore aset of CS values that the UE can select becomes different. Obviously,the network may indicate the same RACH preamble format, e.g., designatea preamble format only by a number of preamble formats 1/2/3/4/5 inTable 9 to Table 12, and differently designate and signal a CS value ofeach format according to coverage supported by the gNB.

While the above description of the RACH preamble formats of the presentinvention has been given focusing on a 15 kHz SCS of Table 9, the abovedescription of the present invention is equally applied to preambleformats having other SCSs of Table 10 to Table 12. Obviously, asupported cell radius is scaled down by the length of an SCS.

A preamble format proposed by the present invention may be modifiedusing a few methods described below.

Method 1) A short sequence based RACH preamble is configured to match Ntimes (where N is a natural number greater than 1) the length of OFDMsymbols used for data transmission. If a sequence is repeated a maximumof M times, a RACH preamble may be configured to be equal to or shorterthan a length corresponding to M times the length of the OFDM symbols.Meanwhile, if the sequence is repeated a maximum of K (where K is anatural number greater than M), the RACH preamble is configured to beshorter than K times the length of OFDM symbols. For example, if theRACH preamble is transmitted in a slot consisting of 14 OFDM symbols,the short sequence based RACH preamble is configured such that asequence is repeated M times (e.g., M=2, 4, 6, 12, 14) and a CP is alsoadded to the preamble. In this case, the RACH preamble is divided into aplurality of resources in a slot in time according to the length of theRACH preamble. For example, in a slot consisting of 14 OFDM symbols, aRACH preamble in which the sequence is repeated 6 times may be dividedinto two RACH resources within the slot in time. On the other hand, fora RACH preamble in which a sequence is repeated 12 times, one RACHresource divided within the slot in time may be present. When M=12 and14, a RACH preamble of a shorter length than M times the length of theOFDM symbols is defined. On the other hand, when M=2, 4, and 6, a RACHpreamble having the same length as the length of the OFDM symbols aswell as a RACH preamble having a shorter length than M times the lengthof the OFDM symbols may be defined.

Method 2) A resource of time and frequency durations may be defined fora short sequence based RACH preamble. If M RACH resources are configuredusing time/frequency resources, the RACH resources are preferentiallyconfigured in time.

In a multi-beam environment of NR, a plurality of physicaltime/frequency resources is needed to transmit the RACH preamble. In aspecific slot, a location at which a RACH resource is configured isassociated with the number of repetitions of the RACH preamble. An exactlocation of the RACH resource, i.e., a symbol number, is determinedbased on a slot format in a slot in which the RACH resource isconfigured. If a slot in which the RACH resource is configured isreferred to as a RACH slot, an exact resource location at which the RACHpreamble can be transmitted is determined with respect to each RACHpreamble format according to a slot type of the RACH slot. The RACH slottype may be indicated to the UE through a RACH configuration andsemi-statically fixed. Herein, indication of the RACH slot type meansindicating the number and locations of symbols on which a DL controlchannel and a UL control channel can be transmitted in a correspondingslot and may be understood as indication of a slot format. The locationsand number of RACH resources in a slot are determined by the RACHconfiguration.

FIGS. 33 to 35 illustrate locations of RACH resources in a slotaccording to RACH slot types. The RACH slot types proposed in FIGS. 33to 35 are purely exemplary and the RACH resources may be started at anytimings of a corresponding slot, designated by a system, in addition tostarting locations illustrated in FIGS. 33 to 35.

Referring to FIGS. 33 to 35, upon signaling RACH resources to the UE,the gNB provides the UE with information about a slot type of a slot towhich each RACH resource belongs, the location of each RACH resource inthe slot, and the number of OFDM symbols. The network needs to configureone or more RACH resources (i.e., RACH time/frequency resources) andinform the UE that the RACH resources are configured. Herein, a RACHresource refers to a time/frequency resource in which one RACH preambleformat can be transmitted. A RACH preamble format used with respect toeach RACH resource should be designated and signaled. As can beappreciated from Table 9 to Table 12, an OFDM symbol length of a RACHresource is determined by the RACH preamble format and the UE may beaware of the symbol length (i.e., the number of OFDM symbols) of theRACH resource using information about the RACH preamble formatdesignated according to each RACH resource. In Table 9 to Table 12illustrating preamble formats according to the present invention, asymbol duration of each preamble format means the length of thepreamble, more precisely, the number of OFDM symbols occupied by acorresponding preamble format through repetition of the preamble.However, there is no reason that a duration of a RACH preamble used inan idle state for initial access is differently configured according toeach RACH resource even if the network configures a plurality of RACHresources. This is because, since maximum cell coverage supported by acorresponding cell should be supported, there is no reason that apreamble duration in any RACH resource is configured to be long and apreamble duration in another RACH resource is configured to be short.Therefore, if the preamble duration is configured to be equal withrespect to each RACH resource, the gNB may commonly designate thepreamble format for RACH resources without designating a preamble formatfor each RACH resource. Alternatively, RACH resources may be dividedinto RACH resource groups (e.g., a long RACH preamble group and a shortRACH preamble group) and a preamble format may be designated withrespect to each RACH resource group. When the preamble format iscommonly designated with respect to RACH resources or is designated withrespect to each RACH resource group, the network may signal one ofpreamble formats 1, 2, 3, 4, and 5, as described with reference to Table9 to Table 12. For example, if a preamble format signaled by the networkis 2, one RACH resource consists of 4 symbols. If three RACH resourceseach having a 4-OFDM symbol length are reserved, a preamble format inthe preceding first and second RACH resources among the three RACHresources which are consecutively subjected to time divisionmultiplexing (TDM) may forcibly apply to preamble A (A1 or A2) and apreamble format in the last RACH resource of a RACH block may forciblyapply to format B. That is, when the RACH preamble is transmitted in thelast RACH resource of the RACH block, the gNB causes the UE tonecessarily insert a gap duration.

Alternatively, when RACH resources are consecutively present, thenetwork may signal a set of RACH preamble formats with respect to theconsecutively configured RACH resources. For example, when preambleformat 1 is used and three consecutive RACH resources are configured, aRACH preamble format capable of being applied to the RACH resource blockin the form of a set of RACH preamble formats, for example, {A1, B},{A1, A1}, {A2, A2}, or {A2, B}, may be signaled to be equally applied toeach RACH resource block or all RACH resource blocks. If the networksignals a combination of {A1, B}, the UE uses preamble format 1-B in thelast RACH resource among consecutive RACH resources and uses preambleformat 1-A1 in other RACH resource(s) except for the last RACH resource.That is, in the case in which the network signals a combination offormats, for example, a combination of {A1, B}, if a RACH resourceassociated with a detected SS block is not the last RACH resource amongRACH resources of a RACH slot in the time domain, the UE transmits aRACH preamble of preamble format A1 in the associated RACH resource and,if the associated RACH resource is the last RACH resource of the RACHslot, the UE transmits the RACH preamble of preamble format B.

When one or more RACH resources configured by the network are present, aunique index may be assigned to each RACH resource in order to identifyeach RACH resource. Information that should be specified with respect toeach RACH resource index is as follows.

Associated SS block index (or indexes): When there are multipleassociated SS block indexes, preamble sequence resources are separatelysignaled with respect to respective SS blocks.

Sequence resources (e.g., a root index, CSs, etc.) for a RACH preamble:Root index information and CS information of the RACH preamble capableof being used in a corresponding RACH resource are signaled.

RACH preamble format: A preamble format used in a corresponding RACHresource and the length of the RACH resource (e.g., the number ofsymbols) are indicated.

Time domain information: Time information of a corresponding RACHresource. Time domain information may include the following elements:

i. A slot index and a frame number to which a corresponding RACHresource belongs;

ii. Type information of a slot to which a corresponding RACH resourcebelongs, i.e., type information of a RACH slot; and/or

iii. A symbol location in a slot to which a corresponding RACH resourcebelongs. Information indicating a symbol location in a slot to which aRACH resource belongs may be information about a symbol number at whichthe RACH resource is started and a duration of the RACH resource (e.g.,the number of symbols). Alternatively, the information indicating thesymbol location in a slot to which the RACH resource belongs may beinformation indicating the location of a RACH resource in order within aRACH slot. The number of RACH resources and the number of symbols withinthe RACH slot may be inferred by the UE through the RACH preamble formatand the UE may identify, through the above type information of the RACHslot, a location of a symbol at which the RACH resource is started in aslot. This information, for example, a RACH resource unit number in aslot (i.e. a RACH resource in a RACH slot) with reference to FIGS. 33 to35, may be signaled as follows according to the length (i.e., duration)of the RACH preamble format:

(a) omittable in the case of a 12-symbol preamble format

(b) 1 bit (0 or 1) in the case of a 6-symbol preamble format

(c) 2 bits in the case of a 4-symbol preamble format

(d) 2 bits in the case of a 3-symbol preamble format

(e) 3 bits in the case of a 2-symbol preamble format

(f) 4 bits in the case of a 1-symbol preamble format

Frequency domain information: Frequency location information of acorresponding RACH resource. For the purpose of indicating a referencepoint of a frequency location of a RACH resource, information about thelowest (or highest) frequency location at which the RACH resource can belocated may be signaled. For example, the above-described frequencylocation at which a RACH resource block is started is signaled. Thefrequency location information of the RACH resource may be signaled asRACH resource common information within a RACH configuration. Bandwidthof the RACH resource, i.e., a RACH bandwidth, is signaled.Alternatively, a subband size of the RACH resource, i.e., the RACHbandwidth, may be determined depending upon a RACH preamble format. ARACH bandwidth when a long sequence based preamble is used and a RACHbandwidth when a short sequence based preamble is used may bedifferently determined. That is, if a preamble format is signaled withrespect to each RACH resource or each RACH resource group, the UE mayeasily identify the RACH bandwidth of the long sequence based preambleand the RACH bandwidth of the short sequence based preamble, inconsideration of an SCS.

FIG. 36 is a block diagram illustrating elements of a transmittingdevice 10 and a receiving device 20 for implementing the presentinvention.

The transmitting device 10 and the receiving device 20 respectivelyinclude Radio Frequency (RF) units 13 and 23 capable of transmitting andreceiving radio signals carrying information, data, signals, and/ormessages, memories 12 and 22 for storing information related tocommunication in a wireless communication system, and processors 11 and21 operationally connected to elements such as the RF units 13 and 23and the memories 12 and 22 to control the elements and configured tocontrol the memories 12 and 22 and/or the RF units 13 and 23 so that acorresponding device may perform at least one of the above-describedembodiments of the present invention.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally control the overall operation ofvarious modules in the transmitting device and the receiving device.Especially, the processors 11 and 21 may perform various controlfunctions to implement the present invention. The processors 11 and 21may be referred to as controllers, microcontrollers, microprocessors, ormicrocomputers. The processors 11 and 21 may be implemented by hardware,firmware, software, or a combination thereof. In a hardwareconfiguration, application specific integrated circuits (ASICs), digitalsignal processors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), or field programmable gate arrays(FPGAs) may be included in the processors 11 and 21. Meanwhile, if thepresent invention is implemented using firmware or software, thefirmware or software may be configured to include modules, procedures,functions, etc. performing the functions or operations of the presentinvention. Firmware or software configured to perform the presentinvention may be included in the processors 11 and 21 or stored in thememories 12 and 22 so as to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 10 performs predeterminedcoding and modulation for a signal and/or data scheduled to betransmitted to the outside by the processor 11 or a scheduler connectedwith the processor 11, and then transfers the coded and modulated datato the RF unit 13. For example, the processor 11 converts a data streamto be transmitted into K layers through demultiplexing, channel coding,scrambling, and modulation. The coded data stream is also referred to asa codeword and is equivalent to a transport block which is a data blockprovided by a MAC layer. One transport block (TB) is coded into onecodeword and each codeword is transmitted to the receiving device in theform of one or more layers. For frequency up-conversion, the RF unit 13may include an oscillator. The RF unit 13 may include Nt (where Nt is apositive integer) transmit antennas.

A signal processing process of the receiving device 20 is the reverse ofthe signal processing process of the transmitting device 10. Undercontrol of the processor 21, the RF unit 23 of the receiving device 20receives radio signals transmitted by the transmitting device 10. The RFunit 23 may include Nr (where Nr is a positive integer) receive antennasand frequency down-converts each signal received through receiveantennas into a baseband signal. The processor 21 decodes anddemodulates the radio signals received through the receive antennas andrestores data that the transmitting device 10 intended to transmit.

The RF units 13 and 23 include one or more antennas. An antenna performsa function for transmitting signals processed by the RF units 13 and 23to the exterior or receiving radio signals from the exterior to transferthe radio signals to the RF units 13 and 23. The antenna may also becalled an antenna port. Each antenna may correspond to one physicalantenna or may be configured by a combination of more than one physicalantenna element. The signal transmitted from each antenna cannot befurther deconstructed by the receiving device 20. An RS transmittedthrough a corresponding antenna defines an antenna from the view pointof the receiving device 20 and enables the receiving device 20 to derivechannel estimation for the antenna, irrespective of whether the channelrepresents a single radio channel from one physical antenna or acomposite channel from a plurality of physical antenna elementsincluding the antenna. That is, an antenna is defined such that achannel carrying a symbol of the antenna can be obtained from a channelcarrying another symbol of the same antenna. An RF unit supporting aMIMO function of transmitting and receiving data using a plurality ofantennas may be connected to two or more antennas. In the presentinvention, the RF unit is also referred to as a transceiver.

In the present invention, the RF units 13 and 23 may support Rx BF andTx BF. For example, in the present invention, the RF units 13 and 23 maybe configured to perform the function illustrated in FIG. 3.

In the embodiments of the present invention, a UE operates as thetransmitting device 10 in UL and as the receiving device 20 in DL. Inthe embodiments of the present invention, a gNB operates as thereceiving device 20 in UL and as the transmitting device 10 in DL.Hereinafter, a processor, a transceiver, and a memory included in the UEwill be referred to as a UE processor, a UE transceiver, and a UEmemory, respectively, and a processor, a transceiver, and a memoryincluded in the gNB will be referred to as a gNB processor, a gNBtransceiver, and a gNB memory, respectively.

The gNB processor of the present invention controls the gNB transceiverto transmit RACH configuration information according to the presentinvention. The RACH configuration information may indicate a preambleformat. The preamble format is one of preamble formats according to thepresent invention. The RACH configuration information may includeinformation indicating a slot in which a RACH preamble can betransmitted, i.e., a slot in which a RACH resource is configured(hereinafter, a RACH slot). The RACH slot information may includeinformation indicating the number of RACH time resources within the RACHslot. The RACH configuration information may include preamble sequenceinformation capable of being used in the RACH resource. The gNBprocessor may control the gNB transceiver to receive a signal in theRACH resource within the RACH slot. The gNB processor may attempt todetect the RACH preamble according to a preamble format corresponding tothe RACH resource. For example, if the RACH configuration informationindicates preamble format 1-A1 (Table 9 to Table 12), the gNB processormay attempt to detect a RACH preamble corresponding to preamble format1-A1. As another example, if the RACH configuration informationindicates a preamble format which is a combination of preamble formatsA1 and B proposed in the present invention, the gNB processor mayattempt to detect the RACH preamble according to preamble format A1 in aRACH resource other than the last RACH resource among consecutive RACHresources in the RACH slot and attempt to detect the RACH preambleaccording to preamble B in the last RACH resource.

The UE transceiver of the present invention receives the RACHconfiguration information and the UE processor controls the UEtransceiver to transmit the RACH preamble based on the RACHconfiguration information. For example, if the UE transceiver receivesthe RACH configuration information including preamble format informationindicating preamble format A1 proposed in the present invention, the UEprocessor controls the UE transceiver to transmit a RACH preamble ofpreamble format A1. The RACH preamble includes a CP part and a sequencepart in the time domain. The UE processor generates the RACH preamble tomatch a preamble format according to the preamble formation informationin the RACH configuration information and controls the UE transceiver totransmit the RACH preamble. For example, if the preamble formatindicated by the RACH configuration information is preamble format A1,the UE processor may generate the RACH preamble such that a CP length ofthe RACH preamble is N times a CP length N_(CP) of an OFDM symbol fordata using the same SCS as an SCS used for the RACH preamble. Herein, Nmay be a value greater than 1, indicating the number of OFDM symbolsused for RACH preamble transmission. For example, referring to Table 9to Table 12, the UE processor may generate the RACH preamble such thatN=2 upon receiving RACH configuration information indicating preambleformat 1-A1, N=4 upon receiving RACH configuration informationindicating preamble format 2-A1, and N=6 upon receiving RACHconfiguration information indicating preamble format 3-A1. The length ofa sequence part of the RACH preamble increases in proportion to N. TheUE processor may generate the sequence part that includes a length-139ZC sequence N times. In the case of preamble format A1 or A2 in thepresent invention, the UE processor may generate the RACH preamble suchthat the length of the RACH preamble is to be N times the length of anOFDM symbol used for data having the same SCS as an SCS used for theRACH preamble. The UE processor may control the UE transceiver totransmit the RACH preamble aligned with a boundary of N OFDM symbolsused for data. For example, the UE processor may generate the RACHpreamble such that the RACH preamble of preamble format A1 is equal to atotal length of N OFDM symbols used to transmit the RACH preamble andcontrols the UE transceiver to transmit the RACH preamble at a timing atwhich the set of the N OFDM symbols are started.

The preamble information in the RACH configuration information mayindicate a combination of preamble format A1 or A2 and preamble formatB. For example, if a combination of preamble format 1-A1 and preambleformat 1-B is indicated, the UE generates a RACH preamble according topreamble format 1-A1 when an RACH resource to be used for RACHtransmission is not the last RACH resource in the time domain of a RACHslot and controls the UE transceiver to transmit the RACH preamble inthe RACH resource. In contrast, the UE generates a RACH preambleaccording to preamble format 1-B when the RACH resource used for RACHtransmission is the last RACH resource in the time domain of the RACHslot and controls the UE transceiver to transmit the RACH preamble inthe RACH resource. The UE processor controls the UE transceiver totransmit the RACH preamble in a RACH resource linked to an SS blockdetected in a cell. A plurality of SS blocks may be transmitted in acell. The UE processor may select an SS block according to a specificcriterion from among detected SS block(s) and use a RACH resourceassociated with the selected SS block for transmission of the RACHpreamble.

As described above, the detailed description of the preferredembodiments of the present invention has been given to enable thoseskilled in the art to implement and practice the invention. Although theinvention has been described with reference to exemplary embodiments,those skilled in the art will appreciate that various modifications andvariations can be made in the present invention without departing fromthe spirit or scope of the invention described in the appended claims.Accordingly, the invention should not be limited to the specificembodiments described herein, but should be accorded the broadest scopeconsistent with the principles and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

While the method of transmitting a RACH and the apparatus therefor havebeen described focusing on an example applied to the 5G NewRAT system,the method and apparatus are applicable to various wirelesscommunication systems in addition to the 5G NewRAT system.

The invention claimed is:
 1. A method of transmitting a random accesschannel (RACH) preamble by a user equipment in a wireless communicationsystem, the method comprising: receiving information on a configurationincluding preamble format information indicating a first format for theRACH preamble; and transmitting the RACH preamble in N orthogonalfrequency division multiplexing (OFDM) symbols based on the first formatfor the RACH preamble, wherein the first format for the RACH preambleincludes only a cyclic prefix (CP) part and a sequence part in a timedomain, and wherein the first format for the RACH preamble satisfies: alength of the CP part is equal to N*N_(CP), where N is greater than 1and N_(CP) is a CP length of an OFDM symbol, and the length of the CPpart plus a length of the sequence part is equal to a total length ofthe N OFDM symbols.
 2. The method according to claim 1, wherein thelength of the CP part is N*144*T_(s) and the length of the sequence partis N*2048*T_(s), where T_(s) is a sampling time.
 3. The method accordingto claim 2, wherein 144*T_(s) is equal to N_(CP) and 2048*T_(s) is equalto a length of a data part per OFDM symbol.
 4. The method according toclaim 1, wherein N is 2, 4, or
 6. 5. The method according to claim 1,wherein the sequence part includes a preamble sequence with a sequencelength of 139 N times.
 6. The method according to claim 1, wherein theinformation on the configuration further includes information on a slotused for a RACH, wherein when the preamble format information indicatesa combination of the first format and a second format, the userequipment transmits the RACH preamble with the first format in a RACHresource associated with a synchronization signal (SS) block detected bythe user equipment among RACH resources of the slot if the associatedRACH resource is not a last RACH resource of the slot in the time domainand transmits a RACH preamble with the second format in the associatedRACH resource if the associated RACH resource is the last RACH resourceof the slot, and wherein the second format includes a guard time with nosignal after a sequence part of the second format.
 7. A user equipmentfor transmitting a random access channel (RACH) preamble in a wirelesscommunication system, the user equipment comprising, a transceiver, anda processor configured to control the transceiver, the processorconfigured to: control the transceiver to receive information on aconfiguration including preamble format information indicating a firstformat for the RACH preamble; and control the transceiver to transmitthe RACH preamble in N orthogonal frequency division multiplexing (OFDM)symbols based on the first format for the RACH preamble, wherein thefirst format for the RACH preamble includes only a cyclic prefix (CP)part and a sequence part in a time domain, and wherein the first formatfor the RACH preamble satisfies: a length of the CP part is equal toN*N_(CP), where N is greater than 1 and N_(CP) is a CP length of an OFDMsymbol, and the length of the CP part plus a length of the sequence partis equal to a total length of the N OFDM symbols.
 8. The user equipmentaccording to claim 7, wherein the length of the CP part is N*144*T_(s)and the length of the sequence part is N*2048*T_(s), where T_(s) is asampling time.
 9. The user equipment according to claim 7, wherein theinformation on the configuration further includes information on a slotused for a RACH, wherein when the preamble format information indicatesa combination of the first format and a second format, the processorcontrols the transceiver to transmit the RACH preamble with the firstformat in a RACH resource associated with a synchronization signal (SS)block detected by the user equipment among RACH resources of the slot ifthe associated RACH resource is not a last RACH resource of the slot inthe time domain and controls the transceiver to transmit a RACH preamblewith the second format in the associated RACH resource if the associatedRACH resource is the last RACH resource of the slot, and the secondformat includes a guard time with no signal after a sequence part of thesecond format.
 10. A method of receiving a random access channel (RACH)preamble by a base station in a wireless communication system, themethod comprising: transmitting information on a configuration includingpreamble format information indicating a first format for the RACHpreamble; and detecting the RACH preamble in N orthogonal frequencydivision multiplexing (OFDM) symbols based on the first format for theRACH preamble, wherein the first format for the RACH preamble includesonly a cyclic prefix (CP) part and a sequence part in a time domain, andwherein the first format for the RACH preamble satisfies: a length ofthe CP part is equal to N*N_(CP), where N is greater than 1 and N_(CP)is a CP length of an OFDM symbol, and the length of the CP part plus alength of the sequence part is equal to a total length of the N OFDMsymbols.
 11. The method according to claim 10, wherein the length of theCP part is N*144*T_(s) and the length of the sequence part isN*2048*T_(s), where T_(s) is a sampling time.
 12. The method accordingto claim 10, wherein the sequence part includes a preamble sequence witha sequence length of 139 N times.
 13. A base station for receiving arandom access channel (RACH) preamble in a wireless communicationsystem, the base station comprising, a transceiver, and a processorconfigured to control the transceiver, the processor configured to:control the transceiver to transmit information on a configurationincluding preamble format information indicating a first format for theRACH format; and detect the RACH preamble in N orthogonal frequencydivision multiplexing (OFDM) symbols based on the first format for theRACH preamble, wherein the first format for the RACH preamble includesonly a cyclic prefix (CP) part and a sequence part in a time domain, andwherein the first format for the RACH preamble satisfies: a length ofthe CP part is equal to N*N_(CP), where N is greater than 1 and N_(CP)is a CP length of an OFDM symbol, and the length of the CP part plus alength of the sequence part is equal to a total length of the N OFDMsymbols.
 14. The base station according to claim 13, wherein the lengthof the CP part is N*144*T_(s) and the length of the sequence part isN*2048*T_(s), where T_(s) is a sampling time.